vsscanf(const char *,const char *,va_list) in P.I.P.S. Open_Environment

Interface status:

externallyDefinedApi

__SLBF 0x0001

Description

line buffered

Interface status:

externallyDefinedApi

__SNBF 0x0002

Description

unbuffered

Interface status:

externallyDefinedApi

__SRD 0x0004

Description

OK to read

Interface status:

externallyDefinedApi

__SWR 0x0008

Description

OK to write

Interface status:

externallyDefinedApi

__SRW 0x0010

Description

open for reading & writing

Interface status:

externallyDefinedApi

__SEOF 0x0020

Description

found EOF

Interface status:

externallyDefinedApi

__SERR 0x0040

Description

found error

Interface status:

externallyDefinedApi

__SMBF 0x0080

Description

_buf is from malloc

Interface status:

externallyDefinedApi

__SAPP 0x0100

Description

fdopen(int,const char *)fdopen(int,const char *)ed in append mode

Interface status:

externallyDefinedApi

__SSTR 0x0200

Description

this is an sprintf or snprintf string

Interface status:

externallyDefinedApi

__SOPT 0x0400

Description

do fseek(FILE *,long,int)fseek(FILE *,long,int) optimization

Interface status:

externallyDefinedApi

__SNPT 0x0800

Description

do not do fseek(FILE *,long,int)fseek(FILE *,long,int) optimization

Interface status:

externallyDefinedApi

__SOFF 0x1000

Description

set iff _offset is in fact correct

Interface status:

externallyDefinedApi

__SMOD 0x2000

Description

true; fgetln modified _p text

Interface status:

externallyDefinedApi

__SALC 0x4000

Description

allocate string space dynamically

Interface status:

externallyDefinedApi

__SIGN 0x8000

Description

ignore this file in _fwalk

Interface status:

externallyDefinedApi

_IOFBF 0

Description

setvbuf should set fully buffered

Interface status:

externallyDefinedApi

_IOLBF 1

Description

setvbuf should set line buffered

Interface status:

externallyDefinedApi

_IONBF 2

Description

setvbuf should set unbuffered

Interface status:

externallyDefinedApi

BUFSIZ 1024

Description

size of buffer used by setbuf

Interface status:

externallyDefinedApi

EOF (-1)

Description

End of file

Interface status:

externallyDefinedApi

FOPEN_MAX 20

Description

must be less than OPEN_MAX

Interface status:

externallyDefinedApi

FILENAME_MAX 256

Description

must be less than PATH_MAX

Interface status:

externallyDefinedApi

L_tmpnam 256

Description

must be == PATH_MAX

Interface status:

externallyDefinedApi

TMP_MAX 308915776

Description

temporary max value

Interface status:

externallyDefinedApi

stdin (__stdin())

Description

standard input variable

Interface status:

externallyDefinedApi

stdout (__stdout())

Description

standard output variable

Interface status:

externallyDefinedApi

stderr (__stderr())

Description

standard error variable

Interface status:

externallyDefinedApi

L_cuserid 17

Description

size for cuserid(3)

Interface status:

externallyDefinedApi

L_ctermid 256

Description

size for ctermid(3)

Interface status:

externallyDefinedApi

__isthreaded (*isthreaded())

Description

defined to isthreaded(void)

Interface status:

externallyDefinedApi

feof (p) (!__isthreaded ? __sfeof(p) : (feof)(p))

Description

Functions defined in ANSI C standard.

Parameters

p

Interface status:

externallyDefinedApi

ferror (p) (!__isthreaded ? __sferror(p) : (ferror)(p))

Description

Functions defined in ANSI C standard.

Parameters

p

Interface status:

externallyDefinedApi

clearerr (p) (!__isthreaded ? __sclearerr(p) : (clearerr)(p))

Description

Functions defined in ANSI C standard.

Parameters

p

Interface status:

externallyDefinedApi

fileno (p) (!__isthreaded ? __sfileno(p) : (fileno)(p))

Description

Functions defined in ANSI C standard.

Parameters

p

Interface status:

externallyDefinedApi

getc (fp) (!__isthreaded ? __sgetc(fp) : (getc)(fp))

Description

Functions defined in ANSI C standard.

Parameters

fp

Interface status:

externallyDefinedApi

getchar (void) getc(stdin)

Description

Defined to getc

Parameters

void

Interface status:

externallyDefinedApi

putchar (x) putc(x, stdout)

Description

defined to putc

Parameters

x

Interface status:

externallyDefinedApi

typedef __off_t fpos_t;

Description

Represents file position

IMPORT_C char* tmpdirname(void);

Description

Note:String that the function will return is not to be modified.

Examples:

/* Illustrates how to use tmpdirname() API */
#include <stdio.h>
int main()
    {
    char *ptr;
    ptr=tmpdirname();
    printf("%s\n",ptr);
    return 0;  
    }

Return value

char *

Upon successful completion tmpdirname(void)tmpdirname(void) will return the path of the private directory of that process.

Interface status:

externallyDefinedApi

IMPORT_C void clearerr(FILE *);

Description

The function clearerr clears the end-of-file and error indicators for the stream pointed to by fp.

The function feof tests the end-of-file indicator for the stream pointed to by fp, returning non-zero if it is set. The end-of-file indicator can only be cleared by the function clearerr.

The function ferror tests the error indicator for the stream pointed to by fp, returning non-zero if it is set. The error indicator can only be reset by the clearerr function.

The function fileno examines the argument fp and returns its integer descriptor.

Examples:

/* this program shows finding error set using ferror 
 and clearing it using clearerr functions */
# 26 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main()
{
        char a;
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", '
');
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        fp=fopen("c:\input.txt","r");
        if (fp ==  0 )
                {
                printf("fopen failed");
                return -1;
                }
        else
                {
                fwrite(&a;, sizeof(char), 1, fp);
                if ((! (*isthreaded())  ? ((( fp )->_flags &  0x0040 ) != 0) : (ferror)( fp )))
                        printf("error set in file stream");
                else
                        {
                        fclose(fp);
                        return -1;
                        }
                (! (*isthreaded())  ? ((void)(( fp )->_flags &= ~( 0x0040 | 0x0020 ))) : (clearerr)( fp ));
                if (!(! (*isthreaded())  ? ((( fp )->_flags &  0x0040 ) != 0) : (ferror)( fp )))
                        printf("error cleared in file stream");
                else printf("error still unexpected set in file stream");
                fclose (fp);
                }
        return 0;
}

Output

error set in file stream
error cleared in file stream

Parameters


                                 				__sFILE__sFILE *

Note: This description also covers the following functions - feof ferror fileno

Interface status:

externallyDefinedApi

IMPORT_C int fclose(FILE *);

Description

The fclose function dissociates the named stream from its underlying file or set of functions. If the stream was being used for output any buffered data is written first using fflush .

Examples:

/* this program shows opening and closing of a file using fclose api */
# 89 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main()
{
        FILE *fp;
        fp = fopen("c:\input.txt", "w+");
        if(fp ==  0 )
                {               
                printf("file opening failed");
                return -1;
                }
        
        printf("file opened successfully: Perform file operations now
");
        
        if(!fclose(fp))
                {
                printf("file closed successfully");
                return 0;
                }
        else
                {
                printf("file closing failed");
                return -1;
                }
}

Output

file opened successfully: Perform file operations now
file closed successfully

Notes:

The fclose function does not handle 0 arguments; they will result in a segmentation violation. This is intentional - it makes it easier to make sure programs written under are bug free. This behaviour is an implementation detail and programs should not rely upon it.

Parameters


                                 				__sFILE__sFILE *

Return value

int

Upon successful completion 0 is returned. Otherwise, EOF is returned and the global variable errno is set to indicate the error. In either case no further access to the stream is possible.

Interface status:

externallyDefinedApi

IMPORT_C int feof(FILE *);

Description

Parameters


                                 				__sFILE__sFILE *

Refer to clearerr for the documentation

Return value

int

Interface status:

externallyDefinedApi

IMPORT_C int ferror(FILE *);

Description

Parameters


                                 				__sFILE__sFILE *

Refer to clearerr for the documentation

Return value

int

Interface status:

externallyDefinedApi

IMPORT_C int fflush(FILE *);

Description

The function fflush forces a write of all buffered data for the given output or update fp via the stream's underlying write function. The open status of the stream is unaffected.

If the fp argument is NULL, fflush flushes all open output streams.

Examples:

/* this program shows flushing user space buffered data using fflush */
# 178 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main()
{
        FILE *fp;
        int retval = 0;
        char name[20] = "c:\flush1.txt";
        fp = fopen(name, "w+"); 
        if(fp ==  0 )
                {               
                printf("Error : File open");
                return -1;
                }
        setvbuf(fp,  0 ,  0 , 100);  // set to full buffering with NULL buffer      
        fprintf(fp, "we are trying to buffer 100 characters at once with NULL buffer.");
        
        retval = fflush(fp);
        if (retval)
                {               
                printf("fflush failed");
                fclose(fp);
                unlink(name);
                return -1;
                }
        else printf("Buffer successfully flushed");
        fclose(fp);
        unlink(name);
        return 0;
}

Output

we are trying to buffer 100 characters at once with  0  buffer.
Buffer successfully flushed

Parameters


                                 				__sFILE__sFILE *

Return value

int

Upon successful completion 0 is returned. Otherwise, EOF is returned and the global variable errno is set to indicate the error.

Description

The fgetc function obtains the next input character (if present) from the stream pointed at by stream, or the next character pushed back on the stream via ungetc.

The getc function acts essentially identically to fgetc, but is a macro that expands in-line.

The getchar function is equivalent to getc (stdin.);

The getw function obtains the next int (if present) from the stream pointed at by stream.

The getc_unlocked and getchar_unlocked functions are equivalent to getc and getchar respectively, except that the caller is responsible for locking the stream with flockfile before calling them. These functions may be used to avoid the overhead of locking the stream for each character, and to avoid input being dispersed among multiple threads reading from the same stream.

Examples:

/* this program shows reading from file using getc */
/* consider input.txt has the following content: */
/* hi */
# 265 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main(void)
{
        int retval;
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", '\n');
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        fp = fopen("C:\input.txt","r");
        if(fp ==  0 )
        {
        printf("fopen failed
");
        return -1;
        }
        while((int)(retval = (! (*isthreaded())  ? (--( fp )->_r < 0 ? __srget( fp ) : (int)(*( fp )->_p++)) : (getc)( fp )) )!=  (-1) )
        {
        printf("%c", retval);
        }
        fclose(fp);
        return 0;
}

Output

hi

Parameters


                                 				__sFILE__sFILE *

Note: This description also covers the following functions - getc getc_unlocked(FILE *)getc_unlocked(FILE *) getchar getchar_unlocked(void)getchar_unlocked(void) getw(FILE *)getw(FILE *)

Return value

int

If successful, these routines return the next requested object from the stream. Character values are returned as an unsigned char converted to an int. If the stream is at end-of-file or a read error occurs, the routines return EOF. The routines and ferror must be used to distinguish between end-of-file and error. If an error occurs, the global variable errno is set to indicate the error. The end-of-file condition is remembered, even on a terminal, and all subsequent attempts to read will return EOF until the condition is cleared with

Description

Parameters

`__sFILE__sFILE *`
`fpos_tfpos_t *`	Refer to `fseek(FILE ,long,int)fseek(FILE ,long,int)` for the documentation

Return value

int

Description

The fgets function reads at most one less than the number of characters specified by n from the given stream and stores them in the string buf. Reading stops when a newline character is found, at end-of-file or error. The newline, if any, is retained. If any characters are read, and there is no error, a \0 character is appended to end the string.

The gets function is equivalent to fgets with an infinite size and a stream of stdin, except that the newline character (if any) is not stored in the string. It is the caller's responsibility to ensure that the input line,if any, is sufficiently short to fit in the string.

Examples:

/* this program shows reading characters from a file using fgets */
/* consider input.txt has the following content: */
/* abcdefghijklmn */
/* fdsfdsafsdabcdefghijklmn */
# 349 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main(void)
{
        char buf[20];
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", "
");
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
                
        fp = fopen("C:\input.txt","r");
        if(fp ==  0 )
                {
                printf("fopen failed");
                return -1;
                }
        if(fgets(buf,18,fp) !=  0 )
                printf("%s", buf);
        else
                printf("Buffer is empty");
        
        buf[0] = '\0';
        if(fgets(buf,2,fp) !=  0 )
                printf("%s", buf);
        else
                printf("Buffer is empty");
        fclose(fp);     
        return 0;
}

Output

abcdefghijklmn
fdsfdsafsdabcdefghijklmn

Security considerations:

The gets function cannot be used securely. Because of its lack of bounds checking,and the inability for the calling program to reliably determine the length of the next incoming line,the use of this function enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. It is strongly suggested that the fgets function be used in all cases.

Parameters

`char *`
`int`
`__sFILE__sFILE *`	Note: This description also covers the following functions - `gets(char )gets(char )`

Return value

char *

Upon successful completion fgets and gets return a pointer to the string. If end-of-file occurs before any characters are read they return NULL and the buffer contents remain unchanged. If an error occurs they return NULL and the buffer contents are indeterminate. The fgets and gets functions do not distinguish between end-of-file and error and callers must use feof and ferror to determine which occurred.

Description

The fopen function opens the file whose name is the string pointed to by file and associates a stream with it.

The argument mode points to a string beginning with one of the following sequences (Additional characters may follow these sequences.):

"r"  Open text file for reading. The stream is positioned at the beginning of the file.
"r+"     Open for reading and writing. The stream is positioned at the beginning of the file.
"w"  Truncate to zero length or create text file for writing. The stream is positioned at the beginning of the file.
"w+"     Open for reading and writing. The file is created if it does not exist, otherwise it is truncated. The stream is positioned at the beginning of the file.
"a"  Open for writing. The file is created if it does not exist. The stream is positioned at the end of the file. Subsequent writes to the file will always end up at the then current end of file, irrespective of any intervening fseek or similar.
"a+"     Open for reading and writing. The file is created if it does not exist. The stream is positioned at the end of the file. Subsequent writes to the file will always end up at the then current end of file, irrespective of any intervening fseek or similar.

The mode string can also include the letter "b" either as a third character or as a character between the characters in any of the two-character strings described above. This is strictly for compatibility with -isoC and has no effect; the "b" is ignored.

Reads and writes may be intermixed on read/write streams in any order, and do not require an intermediate seek as in previous versions of stdio. This is not portable to other systems, however; ANSI C requires that a file positioning function intervene between output and input, unless an input operation encounters end-of-file.

The fdopen function associates a stream with the existing file descriptor, fildes. The mode of the stream must be compatible with the mode of the file descriptor. When the stream is closed via fclose, fildes is closed also.

The freopen function opens the file whose name is the string pointed to by path and associates the stream pointed to by stream with it. The original stream (if it exists) is closed. The mode argument is used just as in the fopen function.

If the file argument is NULL, freopen attempts to re-open the file associated with stream with a new mode. The new mode must be compatible with the mode that the stream was originally opened with:

 Streams originally opened with mode "r" can only be reopened with that same mode.
 Streams originally opened with mode "a" can be reopened with the same mode, or mode "w."
 Streams originally opened with mode "w" can be reopened with the same mode, or mode "a."
 Streams originally opened with mode "r+," "w+," or "a+" can be reopened with any mode.

The primary use of the freopen function is to change the file associated with a standard text stream (stderr, stdin, or stdout).

Examples:

/* this program shows opening  in write mode,write data and close */
/* again open in append mode and write data */
/* Check file c:\fopen.txt */
# 451 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main(void)
{
        FILE *fp;       
        char name[20] = "c:\fopen1.txt";
        
        if ((fp = fopen (name, "w")) ==  0 )
        {
        printf("Error creating file");
        return -1;
        }
        printf("Opened file");
      fprintf(fp, "This is the first line");
      printf("Wrote to file");
      fclose (fp);
      printf("Closed file");
      if ((fp = fopen (name, "a")) ==  0 )
      {
      printf("Error opening file");
      return -1;
      }
      printf("Opened file for appending");
      fprintf(fp, "This is the second line");
      fclose (fp);
      printf("closed file, check output in c:\ fopen.txt file");
      unlink(name);
      return 0;
}

Output

Opened file
Wrote to file
Closed file
Opened file for appending
closed file, check output in c:\fopen.txt file

Notes:

Mode values for group and others are be ignored.
The execute bit and setuid on exec bit are ignored.
The default working directory of a process is initialized to C:\private\UID (UID of the calling application) and any data written into this directory persists between phone resets.
If the specified file is a symbolic link and the file it is pointing to is invalid the symbolic link file will be automatically removed.

Limitations:

A file in cannot be created with write-only permission and attempting to create one will result in a file with read-write permission. Creating a new file with the O_CREAT flag does not alter the time stamp of its parent directory. The newly created entry has only two time stamps: access and modification. Creation time stamp is not supported and access time stamp is initially equal to modification time stamp. open, fclose and fflush.

KErrNotReady of symbian error code is mapped to 2 , which typically means drive not found or filesystem not mounted on the drive.

Parameters

`const char *`
`const char *`	Note: This description also covers the following functions - `fdopen(int,const char )fdopen(int,const char )` `freopen(const char ,const char ,FILE )freopen(const char ,const char ,FILE )`

Return value

__sFILE__sFILE *

Upon successful completion fopen, fdopen and freopen return a FILE pointer. Otherwise, NULL is returned and the global variable errno is set to indicate the error.

Description

Parameters

`__sFILE__sFILE *`
`const char *`
`...`

Return value

int

Description

The fputc function writes the character c (converted to an "unsigned char") to the output stream pointed to by fp.

The putc macro that is identically to fputc, but is a macro that expands in-line. It may evaluate stream more than once, so arguments given to putc should not be expressions with potential side effects.

The putchar function is identical to putc with an output stream of stdout.

The putw function writes the specified int to the named output stream.

The putc_unlocked and putchar_unlocked functions are equivalent to putc and putchar respectively, except that the caller is responsible for locking the stream with flockfile before calling them. These functions may be used to avoid the overhead of locking the stream for each character, and to avoid output being interspersed from multiple threads writing to the same stream.

Examples:

#include <stdio.h>
int main()
{
        FILE * fp;
        fp=fopen("C:\input.txt","w+");
        
        if(fp==NULL)
                {
                printf("file opening failed");
                return -1;
                }
        if(putc('a',fp)!='a')
                {
                printf("putc failed");
                fclose(fp);
                return -1;
                }
        else printf("character successfully put by putc");
        
        fclose(fp);
        return 0;
}

Output

character successfully put by putc

Parameters

`int`
`__sFILE__sFILE *`	Note: This description also covers the following functions - `putc` `putc_unlocked(int,FILE )putc_unlocked(int,FILE )` `putchar` `putchar_unlocked(int)putchar_unlocked(int)` `putw(int,FILE )putw(int,FILE )`

Return value

int

The functions, fputc, putc, putchar, putc_unlocked, and putchar_unlocked return the character written. If an error occurs, the value EOF is returned. The putw function returns 0 on success; EOF is returned if a write error occurs, or if an attempt is made to write to a read-only stream.

Description

The function fputs writes the string pointed to by s to the stream pointed to by fp.

The function puts writes the string s, and a terminating newline character, to the stream stdout.

Examples:

/*this program shows writing characters from a file using fputs */
/* consider input.txt has the following content: */
/* hello world */
# 632 "d:/EPOC/release/9.4/common/generic/openenv/core/include/stdio.dosc" 2
int main(void)
{
        int wretval;    
        char rs1[50],rs2[50];
        char *rptr;
        int retval;
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", "");
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        fp = fopen("c:\input.txt","r");
        if(fp ==  0 )
        {
        printf("fopen failed");
        return -1;
        }
        rptr = fgets(rs1,12,fp);
        if(rptr ==  0 )
        {
        printf("fgets failed");
        fclose(fp);
        return -1;
        }
        fclose(fp);
        fp = fopen("c:\puts1.txt","w+");
        if(fp ==  0 )
        {
        printf("fopen failed");
        return -1;
        }
        wretval = fputs(rs1,fp);
        if(wretval ==  (-1) )
        {
        printf("fputs failed");
        fclose(fp);
        return -1;
        }
        fclose(fp);
        fp = fopen("C:\puts1.txt","r");
        if(fp ==  0 )
        {
        printf("fopen failed");
        return -1;
        }
        rptr = fgets(rs2,12,fp);
        if(rptr ==  0 )
        {
        printf("fgets failed");
        fclose(fp);
        return -1;
        }
        printf("file reading returned \"%s\",rs2);
        fclose(fp);
        unlink("C:\puts1.txt");
        
        return 0;
}

Output

file reading returned "abcdefghijk"

Parameters

`const char *`
`__sFILE__sFILE *`	Note: This description also covers the following functions - `puts(const char )puts(const char )`

Return value

int

The fputs function returns 0 on success and EOF on error. The puts function returns a nonnegative integer on success and EOF on error.

Interface status:

externallyDefinedApi

IMPORT_C size_t fread(void *, size_t, size_t, FILE *);

Description

The function fread reads count objects, each size bytes long, from the stream pointed to by fp, storing them at the location given by buf.

The function fwrite writes count objects, each size bytes long, to the stream pointed to by fp, obtaining them from the location given by buf.

Examples:

/* this program shows reading characters from a file using fread */
/* consider input.txt has the following content: */
/* hi */
#include <stdio.h>
int main()
{
        char a; 
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", '\n');
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        fp = fopen("c:\input.txt", "r");
        if (fp == NULL)
                {
                printf ("fopen failed");
                return -1;
                }
        // read single chars at a time, stopping on EOF or error:
        while (fread(&a;, sizeof(char), 1, fp), !feof(fp) && !ferror(fp))
                {
                printf("I read \"%c\",a);
                }
        if (ferror(fp)) //Some error occurred
                {
                fclose(fp);
                return -1;
                }
        fclose(fp);
        return 0;
}

Output

I read "h"
I read "i"

Parameters

`void *`
`size_tsize_t`
`size_tsize_t`
`__sFILE__sFILE *`	Note: This description also covers the following functions - `fwrite(const void ,size_t,size_t,FILE )fwrite(const void ,size_t,size_t,FILE )`

Return value

size_tsize_t

The functions fread and fwrite advance the file position indicator for the stream by the number of bytes read or written. They return the number of objects read or written. If an error occurs, or the end-of-file is reached, the return value is a short object count (or zero). The function fread does not distinguish between end-of-file and error. Callers must use feof and ferror to determine which occurred. The function fwrite returns a value less than count only if a write error has occurred.

Interface status:

externallyDefinedApi

IMPORT_C FILE* freopen(const char *, const char *, FILE *);

Description

Parameters

`const char *`
`const char *`
`__sFILE__sFILE *`	Refer to `fopen(const char ,const char )fopen(const char ,const char )` for the documentation

Return value

__sFILE__sFILE *

Description

Parameters

`__sFILE__sFILE *`
`const char *`
`...`

Return value

int

Description

The fseek function sets the file position indicator for the stream pointed to by fp. The new position, measured in bytes, is obtained by adding offset bytes to the position specified by whence. If whence is set to SEEK_SET, SEEK_CUR, or SEEK_END, the offset is relative to the start of the file, the current position indicator, or end-of-file, respectively. A successful call to the fseek function clears the end-of-file indicator for the stream and undoes any effects of the ungetc and ungetwc functions on the same stream. The fseek function call does not allows the file offset to be set beyond the end of the existing end-of-file of the file.

The ftell function obtains the current value of the file position indicator for the stream pointed to by fp.

The rewind function sets the file position indicator for the stream pointed to by fp to the beginning of the file. It is equivalent to:

     (void)fseek(fp, 0L, SEEK_SET)

except that the error indicator for the stream is also cleared. Since rewind does not return a value, an application wishing to detect errors should clear errno, then call rewind, and if errno is non-zero, assume an error has occurred. The fgetpos and fsetpos functions are alternate interfaces for retrieving and setting the current position in the file, similar to ftell and fseek, except that the current position is stored in an opaque object of type fpos_t pointed to by pos. These functions provide a portable way to seek to offsets larger than those that can be represented by a long int. They may also store additional state information in the fpos_t object to facilitate seeking within files containing multibyte characters with state-dependent encodings. Although fpos_t has traditionally been an integral type, applications cannot assume that it is; in particular, they must not perform arithmetic on objects of this type. If the stream is a wide character stream, the position specified by the combination of offset and whence must contain the first byte of a multibyte sequence.

Examples:

/* this program shows setting file offset using fseek */
#include <stdio.h>
int main(void)
{       
        int retval;
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", '');
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        fp = fopen("c:\input.txt", "r");
        if (fp == NULL)
        {
        printf ("fopen failed");
        return -1;
        }
        retval = fseek(fp, 3, SEEK_SET); // seek to the 20th byte of the file
        if (retval)
        {
        printf ("fseek failed");
        return -1;
        }
        
        long pos = ftell(fp);
        if (pos ==3)
        {       
        printf("offset setting proper");
        }
        fclose(fp);
        return 0;
}

Output

offset setting proper

Parameters

`__sFILE__sFILE *`
`long`
`int`	Note: This description also covers the following functions - `ftell(FILE )ftell(FILE )` `rewind(FILE )rewind(FILE )` `fgetpos(FILE ,fpos_t )fgetpos(FILE ,fpos_t )` `fsetpos(FILE ,const fpos_t )fsetpos(FILE ,const fpos_t )`

Return value

int

The rewind function returns no value. Upon successful completion ftell returns the current offset. Otherwise -1 is returned and the global variable errno is set to indicate the error.

Description

Parameters

`__sFILE__sFILE *`
`const fpos_tfpos_t *`	Refer to `fseek(FILE ,long,int)fseek(FILE ,long,int)` for the documentation

Return value

int

Description

Parameters


                                 				__sFILE__sFILE *

Refer to fseek(FILE *,long,int)fseek(FILE *,long,int) for the documentation

Return value

long

Description

Parameters

`const void *`
`size_tsize_t`
`size_tsize_t`
`__sFILE__sFILE *`	Refer to `fread(void ,size_t,size_t,FILE )fread(void ,size_t,size_t,FILE )` for the documentation

Return value

size_tsize_t

Interface status:

externallyDefinedApi

IMPORT_C int getc(FILE *);

Description

Parameters


                                 				__sFILE__sFILE *

Refer to fgetc(FILE *)fgetc(FILE *) for the documentation

Return value

int

Description

Parameters

char *

Refer to fgets(char *,int,FILE *)fgets(char *,int,FILE *) for the documentation

Return value

char *

Interface status:

externallyDefinedApi

IMPORT_C void perror(const char *);

Description

The strerror , strerror_r and perror functions look up the error message string corresponding to an error number.

The strerror function accepts an error number argument errnum and returns a pointer to the corresponding message string.

The strerror_r function renders the same result into strerrbuf for a maximum of buflen characters and returns 0 upon success.

The perror function finds the error message corresponding to the current value of the global variable errno and writes it, followed by a newline, to the standard error file descriptor. If the argument string is non- NULL and does not point to the null character, this string is prepended to the message string and separated from it by a colon and space (": "); otherwise, only the error message string is printed.

If the error number is not recognized, these functions return an error message string containing "Unknown error: " followed by the error number in decimal. The strerror and strerror_r functions return EINVAL as a warning. Error numbers recognized by this implementation fall in the range 0 < errnum < sys_nerr .

If insufficient storage is provided in strerrbuf (as specified in buflen ) to contain the error string, strerror_r returns ERANGE and strerrbuf will contain an error message that has been truncated and NUL terminated to fit the length specified by buflen .

The message strings can be accessed directly using the external array sys_errlist . The external value sys_nerr contains a count of the messages in sys_errlist . The use of these variables is deprecated; strerror or strerror_r should be used instead.

Examples:

#include <string.h>
#include <stdio.h>
#include <errno.h>
int main()
{
    char *ptr = strerror(ERANGE);
    printf("strerror( 34 ) = %s",ptr);
    return 0;
}

Output

strerror(ERANGE) = Numerical result out of range

Bugs:

For unknown error numbers, the strerror function will return its result in a static buffer which may be overwritten by subsequent calls. The return type for strerror is missing a type-qualifier; it should actually be const char * . Programs that use the deprecated sys_errlist variable often fail to compile because they declare it inconsistently.

Parameters

const char *

Note: This description also covers the following functions - strerror(int)strerror(int) strerror_r(int,char *,size_t)strerror_r(int,char *,size_t)

Interface status:

externallyDefinedApi

IMPORT_C int printf(const char *,...);

Description

The printf family of functions produces output according to a format as described below. The printf and vprintf functions write output to stdout, the standard output stream; fprintf and vfprintf write output to the given output stream; sprintf, snprintf, vsprintf, and vsnprintf write to the character string str; and asprintf and vasprintf dynamically allocate a new string with malloc.

These functions write the output under the control of a format string that specifies how subsequent arguments (or arguments accessed via the variable-length argument facilities of stdarg ) are converted for output.

These functions return the number of characters printed (not including the trailing '\0' used to end output to strings) or a negative value if an output error occurs, except for snprintf and vsnprintf, which return the number of characters that would have been printed if the size were unlimited (again, not including the final '\0').

The asprintf and vasprintf functions set *ret to be a pointer to a buffer sufficiently large to hold the formatted string. This pointer should be passed to free to release the allocated storage when it is no longer needed. If sufficient space cannot be allocated, asprintf and vasprintf will return -1 and set ret to be a NULL pointer.

The snprintf and vsnprintf functions will write at most size -1 of the characters printed into the output string (the size'th character then gets the terminating '\0' );if the return value is greater than or equal to the size argument, the string was too short and some of the printed characters were discarded. The output is always null-terminated.

The sprintf and vsprintf functions effectively assume an infinite size.

The format string is composed of zero or more directives: ordinary characters (not % ), which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments. Each conversion specification is introduced by the % character. The arguments must correspond properly (after type promotion) with the conversion specifier. After the %, the following appear in sequence:

 An optional field, consisting of a decimal digit string followed by a $, specifying the next argument to access. If this field is not provided, the argument following the last argument accessed will be used. Arguments are numbered starting at 1. If unaccessed arguments in the format string are interspersed with ones that are accessed the results will be indeterminate.
 Zero or more of the following flags:
      '#'    The value should be converted to an "alternate form." For c, d, i, n, p, s, and u conversions, this option has no effect. For o conversions, the precision of the number is increased to force the first character of the output string to a zero (except if a zero value is printed with an explicit precision of zero). For x and X conversions, a non-zero result has the string '0x' (or '0X' for X conversions) prepended to it. For a, A, e, E, f, F, g, and G conversions, the result will always contain a decimal point, even if no digits follow it (normally, a decimal point appears in the results of those conversions only if a digit follows). For g and G conversions, trailing zeros are not removed from the result as they would otherwise be.
      '0(zero)'  Zero padding. For all conversions except n, the converted value is padded on the left with zeros rather than blanks. If a precision is given with a numeric conversion (d, i, o, u, i, x, and X), the 0 flag is ignored.
      '-'    A negative field width flag; the converted value is to be left adjusted on the field boundary. Except for n conversions, the converted value is padded on the right with blanks, rather than on the left with blanks or zeros. A - overrides a 0 if both are given.
      ' (space)'    A blank should be left before a positive number produced by a signed conversion (a, A, d, e, E, f, F, g, G, or i).
      '+'    A sign must always be placed before a number produced by a signed conversion. A + overrides a space if both are used.
      '''    Decimal conversions (d, u, or i) or the integral portion of a floating point conversion (f or F) should be grouped and separated by thousands using the non-monetary separator returned by localeconv.
 An optional decimal digit string specifying a minimum field width. If the converted value has fewer characters than the field width, it will be padded with spaces on the left (or right, if the left-adjustment flag has been given) to fill out the field width.
 An optional precision, in the form of a period . followed by an optional digit string. If the digit string is omitted, the precision is taken as zero. This gives the minimum number of digits to appear for d, i, o, u, x, and X conversions, the number of digits to appear after the decimal-point for a, A, e, E, f, and F conversions, the maximum number of significant digits for g and G conversions, or the maximum number of characters to be printed from a string for s conversions.
 An optional length modifier, that specifies the size of the argument. The following length modifiers are valid for the d, i, n, o, u, x, or X conversion:

      Modifier        d, i              o, u, x, X                n
      hh              signed char       unsigned char             signed char *
      h               short             unsigned short            short *
      l (ell)         long              unsigned long             long *
      ll (ell ell)    long long         unsigned long long        long long *
      j               intmax_t          uintmax_t                 intmax_t *
      t               ptrdiff_t         (see note)                ptrdiff_t *
      z               (see note)        size_t                    (see note)
      q (deprecated)  quad_t            u_quad_t                  quad_t *    


      Note: the t modifier, when applied to a o, u, x, or X conversion, indicates that the argument is of an unsigned type equivalent in size to a ptrdiff_t. The z modifier, when applied to a d or i conversion, indicates that the argument is of a signed type equivalent in size to a size_t. Similarly, when applied to an n conversion, it indicates that the argument is a pointer to a signed type equivalent in size to a size_t.

      The following length modifier is valid for the a, A, e, E, f, F, g, or G conversion:

      Modifier    a, A, e, E, f, F, g, G
      l (ell)     double (ignored, same behavior as without it)
      L           long double


      The following length modifier is valid for the c or s conversion:

      Modifier    c         s
      l (ell)     wint_t    wchar_t *


 A character that specifies the type of conversion to be applied. 

A field width or precision, or both, may be indicated by an asterisk '*' or an asterisk followed by one or more decimal digits and a '\$' instead of a digit string. In this case, an int argument supplies the field width or precision. A negative field width is treated as a left adjustment flag followed by a positive field width; a negative precision is treated as though it were missing. If a single format directive mixes positional (nn$) and non-positional arguments, the results are undefined.

The conversion specifiers and their meanings are:
diouxX
   The int (or appropriate variant) argument is converted to signed decimal (d and i), unsigned octal (o,) unsigned decimal (u,) or unsigned hexadecimal (x and X) notation. The letters "abcdef" are used for x conversions; the letters "ABCDEF" are used for X conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros.
DOU    The long int argument is converted to signed decimal, unsigned octal, or unsigned decimal, as if the format had been ld, lo, or lu respectively. These conversion characters are deprecated, and will eventually disappear.
eE     The double argument is rounded and converted in the style [-d . ddd e \*[Pm] dd] where there is one digit before the decimal-point character and the number of digits after it is equal to the precision; if the precision is missing, it is taken as 6; if the precision is zero, no decimal-point character appears. An E conversion uses the letter 'E' (rather than 'e') to introduce the exponent. The exponent always contains at least two digits; if the value is zero, the exponent is 00.

For a, A, e, E, f, F, g, and G conversions, positive and negative infinity are represented as inf and -inf respectively when using the lowercase conversion character, and INF and -INF respectively when using the uppercase conversion character. Similarly, NaN is represented as nan when using the lowercase conversion, and NAN when using the uppercase conversion.
fF     The double argument is rounded and converted to decimal notation in the style [-ddd . ddd,] where the number of digits after the decimal-point character is equal to the precision specification. If the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. If a decimal point appears, at least one digit appears before it.
gG     The double argument is converted in style f or e (or F or E for G conversions). The precision specifies the number of significant digits. If the precision is missing, 6 digits are given; if the precision is zero, it is treated as 1. Style e is used if the exponent from its conversion is less than -4 or greater than or equal to the precision. Trailing zeros are removed from the fractional part of the result; a decimal point appears only if it is followed by at least one digit.
aA     The double argument is rounded and converted to hexadecimal notation in the style [-0x h . hhhp[\*[Pm]d,]] where the number of digits after the hexadecimal-point character is equal to the precision specification. If the precision is missing, it is taken as enough to represent the floating-point number exactly, and no rounding occurs. If the precision is zero, no hexadecimal-point character appears. The p is a literal character 'p' and the exponent consists of a positive or negative sign followed by a decimal number representing an exponent of 2. The A conversion uses the prefix "0X" (rather than "0x"), the letters "ABCDEF" (rather than "abcdef)" to represent the hex digits, and the letter 'P' (rather than 'p') to separate the mantissa and exponent.

Note that there may be multiple valid ways to represent floating-point numbers in this hexadecimal format. For example, 0x3.24p+0, 0x6.48p-1 and 0xc.9p-2 are all equivalent. The format chosen depends on the internal representation of the number, but the implementation guarantees that the length of the mantissa will be minimized. Zeroes are always represented with a mantissa of 0 (preceded by a '-' if appropriate) and an exponent of +0.
C  Treated as c with the l (ell) modifier.
c  The int argument is converted to an unsigned char , and the resulting character is written.

If the l (ell) modifier is used, the wint_t argument shall be converted to a wchar_t, and the (potentially multi-byte) sequence representing the single wide character is written, including any shift sequences. If a shift sequence is used, the shift state is also restored to the original state after the character.
S  Treated as s with the l (ell) modifier.
s  The char * argument is expected to be a pointer to an array of character type (pointer to a string). Characters from the array are written up to (but not including) a terminating NUL character; if a precision is specified, no more than the number specified are written. If a precision is given, no null character need be present; if the precision is not specified, or is greater than the size of the array, the array must contain a terminating NUL character.

If the l (ell) modifier is used, the wchar_t * argument is expected to be a pointer to an array of wide characters (pointer to a wide string). For each wide character in the string, the (potentially multi-byte) sequence representing the wide character is written, including any shift sequences. If any shift sequence is used, the shift state is also restored to the original state after the string. Wide characters from the array are written up to (but not including) a terminating wide NUL character; if a precision is specified, no more than the number of bytes specified are written (including shift sequences). Partial characters are never written. If a precision is given, no null character need be present; if the precision is not specified, or is greater than the number of bytes required to render the multibyte representation of the string, the array must contain a terminating wide NUL character.
p  The void * pointer argument is printed in hexadecimal (as if by '%#x' or '%#lx' ).
n  The number of characters written so far is stored into the integer indicated by the int * (or variant) pointer argument. No argument is converted.
 %    A '%' is written. No argument is converted. The complete conversion specification is '%%'.

The decimal point character is defined in the program's locale (category LC_NUMERIC ).

In no case does a non-existent or small field width cause truncation of a numeric field; if the result of a conversion is wider than the field width, the field is expanded to contain the conversion result.

Examples:

To print a date and time in the form "Sunday, July 3, 10:02", where weekday and month are pointers to strings:

#include <stdio.h>
fprintf(stdout, "%s, %s %d, %.2d:%.2d
",
        weekday, month, day, hour, min);

To print pi to five decimal places:

#include <math.h>
#include <stdio.h>
fprintf(stdout, "pi = %.5f
", 4 * atan(1.0));

To allocate a 128 byte string and print into it:

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
char *newfmt(const char *fmt, ...)
{
        char *p;
        va_list ap;
        if ((p = malloc(128)) == NULL)
                return (NULL);
        va_start(ap, fmt);
        (void) vsnprintf(p, 128, fmt, ap);
        va_end(ap);
        return (p);
}

/* this program shows printing onto the console using printf */
#include <stdio.h>
int main(void)
{
        char * msg="hello world";
        printf("%s",msg);
        return 0;
}

Output

hello world

/* this program shows reading from console using scanf */
#include <stdio.h>
int main(void)
{
        char msg[100];
        printf("enter message to be printed");
        scanf("%s",msg);
        printf("message entered is: %s",msg);
        return 0;
}

Output

enter message to be printed
hello (assuming this is user input)
message entered is: hello

Security considerations:

The sprintf and vsprintf functions are easily misused in a manner which enables malicious users to arbitrarily change a running program's functionality through a buffer overflow attack. Because sprintf and vsprintf assume an infinitely long string, callers must be careful not to overflow the actual space; this is often hard to assure. For safety, programmers should use the snprintf interface instead.

The printf and sprintf family of functions are also easily misused in a manner allowing malicious users to arbitrarily change a running program's functionality by either causing the program to print potentially sensitive data "left on the stack", or causing it to generate a memory fault or bus error by dereferencing an invalid pointer. %n can be used to write arbitrary data to potentially carefully-selected addresses. Programmers are therefore strongly advised to never pass untrusted strings as the format argument, as an attacker can put format specifiers in the string to mangle your stack, leading to a possible security hole. This holds true even if the string was built using a function like snprintf, as the resulting string may still contain user-supplied conversion specifiers for later interpolation by printf. Always use the proper secure idiom:

snprintf(buffer, sizeof(buffer), "%s", string);

Bugs:

The conversion formats %D, %O, and %U are not standard and are provided only for backward compatibility. The effect of padding the %p format with zeros (either by the 0 flag or by specifying a precision), and the benign effect (i.e., none) of the # flag on %n and %p conversions, as well as other nonsensical combinations such as %Ld, are not standard; such combinations should be avoided. The printf family of functions do not correctly handle multibyte characters in the format argument.

Parameters

`const char *`
`...`

Return value

int

Upon successful return, these functions return the number of characters printed (not including the trailing \0 used to end output to strings). The functions snprintf and vsnprintf do not write more than size bytes (including the trailing \0). If the output was truncated due to this limit then the return value is the number of characters (not including the trailing \0) which would have been written to the final string if enough space had been available. Thus, a return value of size or more means that the output was truncated. If an output error is encountered, a negative value is returned.None of these functions support long double length modifiers. Floating point format specifiers support a maximum precision of 15 digits.

Description

Parameters

`int`
`__sFILE__sFILE *`	Refer to `fputc(int,FILE )fputc(int,FILE )` for the documentation

Return value

int

Description

Parameters

int

Refer to fputc(int,FILE *)fputc(int,FILE *) for the documentation

Return value

int

Description

Parameters

const char *

Refer to fputs(const char *,FILE *)fputs(const char *,FILE *) for the documentation

Return value

int

Interface status:

externallyDefinedApi

IMPORT_C int remove(const char *);

Description

The remove function removes the file or directory specified by file.

If file specifies a directory, remove (file); is the equivalent of rmdir (file); Otherwise, it is the equivalent of unlink (file);

Examples:

/* this program shows deleting a file using remove */
#include <stdio.h>
int main()
{
        char *name = "C:\input.txt";
        FILE *fp = fopen(name, "w+");
        if (fp == NULL)
                {
                printf ("fopen failed");
                return -1;
                }
        fprintf(fp,"hello world");
        fclose(fp);
        
        remove(name);
        fp=fopen(name,"r");
        if (fp == NULL)
                {
                printf ("file has been deleted already");
                }
        else
                {
                printf("remove failed");
                return -1;
                }
        
        return 0;
}

Output

file has been deleted already

Limitations:

The file parameter of the remove(const char *)remove(const char *) function should not exceed 256 characters in length.
P.I.P.S. only simulates link files and does not distinguish between hard and symbolic links.
KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive not found or filesystem not mounted on the drive.

Parameters

const char *

Return value

int

Upon successful completion, reomve return 0. Otherwise, -1 is returned and the global variable errno is set to indicate the error.

Description

The rename system call causes the link named oldpath to be renamed as to. If to exists, it is first removed. Both oldpath and newpath must be of the same type (that is, both directories or both non-directories), and must reside on the same file system.

If the final component of oldpath is a symbolic link, the symbolic link is renamed, not the file or directory to which it points.

If a file with a symbolic link pointing to it is renamed, then a subsequent open call on the symbolic link file would automatically remove the link file, i.e consider a symbolic file link.x pointing to a file abc.x. If the file abc.x is renamed to abcd.x then, a subsequent open call on link.x file would automatically remove link.x file.

Note:

rename(const char *,const char *)rename(const char *,const char *) does not differentiate between hard and soft links.
If the specified file is a dangling link file, then this link file will be automatically removed.

Limitations:

The to and from parameters in rename(const char *,const char *)rename(const char *,const char *) shouldn't exceed 256 characters.
The rename(const char *,const char *)rename(const char *,const char *) function fails if either from or to parameters refer to a file in use (that is, if either file is held open by a process).
The parent directory time stamps are not affected when rename(const char *,const char *)rename(const char *,const char *) creates a new entry. The time stamps for the new entry like time of last access is equal to time of last data modification. The time of last file status change for any file would be 0.
KErrNotReady of Symbian error code is mapped to ENOENT, which typically means drive not found or filesystem not mounted on the drive.

Examples:

/*
 Detailed description: This sample code demonstrates usage of rename system call.

 Preconditions: Example.cfg file should be present in the current working directory.
 */
#include <stdio.h>
int main()
{
  if(rename("Example.txt" , "Example2.txt") < 0 )  {
     printf("Failed to rename Example.txt");
     return -1;
  }
  printf("Rename successful");
  return 0;
}

Output

Rename successful

Parameters

`const char *`
`const char *`

Return value

int

The rename(const char *,const char *)rename(const char *,const char *) function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

Description

Parameters


                                 				__sFILE__sFILE *

Refer to fseek(FILE *,long,int)fseek(FILE *,long,int) for the documentation

Description

The scanf family of functions scans input according to a format as described below. This format may contain conversion specifiers; the results from such conversions, if any, are stored through the pointer arguments. The scanf function reads input from the standard input stream stdin, fscanf reads input from the stream pointer stream, and sscanf reads its input from the character string pointed to by str. The vfscanf function is analogous to vfprintf and reads input from the stream pointer stream using a variable argument list of pointers (see stdarg).

The vscanf function scans a variable argument list from the standard input and the vsscanf function scans it from a string; these are analogous to the vprintf and vsprintf functions respectively. Each successive pointer argument must correspond properly with each successive conversion specifier (but see the * conversion below). All conversions are introduced by the % (percent sign) character. The format string may also contain other characters. White space (such as blanks, tabs, or newlines) in the format string match any amount of white space, including none, in the input. Everything else matches only itself. Scanning stops when an input character does not match such a format character. Scanning also stops when an input conversion cannot be made (see below).

Examples:

/* this program shows scanning from file using fscanf */
#include <stdio.h>
int main(void)
{
        char x;
        int ret;
        char* filename="c:\ScanfTest1.txt";
        FILE *fp=fopen(filename,"w");
        fprintf(fp,"%s","abcdesdafg");
        fclose(fp);
        fp=fopen(filename,"r");
        ret=fscanf(fp,"%c",&x;);
        fclose(fp);
        printf("fscanf returned:%c",x);
        unlink(filename);
        getchar();
        if(ret!= 1)
                return -1;
        else
                return 0;
}

Output

fscanf returned:a

Examples:

/* this program shows scanning from file using fscanf */
#include <stdio.h>
int main(void)
{
        char x;
        int ret;
        char* filename="c:\ScanfTest1.txt";
        FILE *fp=fopen(filename,"w");
        fprintf(fp,"%s","abcdesdafg");
        fclose(fp);
        fp=fopen(filename,"r");
        ret=fscanf(fp,"%c",&x;);
        fclose(fp);
        printf("fscanf returned:%c",x);
        unlink(filename);
        getchar();
        if(ret!= 1)
                return -1;
        else
                return 0;
}

Output

fscanf returned:a

Parameters

`const char *`
`...`

Return value

int

These functions return the number of input items assigned, which can be fewer than provided for, or even zero, in the event of a matching failure. Zero indicates that, while there was input available, no conversions were assigned; typically this is due to an invalid input character, such as an alphabetic character for a '%d' conversion. The value EOF is returned if an input failure occurs before any conversion such as an end-of-file occurs. If an error or end-of-file occurs after conversion has begun, the number of conversions which were successfully completed is returned.None of these functions support long double data types.

Description

The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information appears on the destination file or terminal as soon as written; when it is block buffered many characters are saved up and written as a block; when it is line buffered characters are saved up until a newline is output or input is read from any stream attached to a terminal device (typically stdin). The function fflush may be used to force the block out early.

Normally all files are block buffered. When the first I/O operation occurs on a file, malloc is called, and an optimally-sized buffer is obtained. If a stream refers to a terminal (as stdout normally does) it is line buffered. The standard error stream stderr is always unbuffered.

The setvbuf function may be used to alter the buffering behavior of a stream. The mode argument must be one of the following three macros:

_IONBF
   unbuffered
_IOLBF
   line buffered
_IOFBF
   fully buffered

The size argument may be given as zero to obtain deferred optimal-size buffer allocation as usual. If it is not zero, then except for unbuffered files, the buf argument should point to a buffer at least size bytes long; this buffer will be used instead of the current buffer. If buf is not NULL, it is the caller's responsibility to free this buffer after closing the stream.

The setvbuf function may be used at any time, but may have peculiar side effects (such as discarding input or flushing output) if the stream is "active". Portable applications should call it only once on any given stream, and before any I/O is performed.

The other three calls are, in effect, simply aliases for calls to setvbuf. Except for the lack of a return value, the setbuf function is exactly equivalent to the call

     setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);

The setbuffer function is the same, except that the size of the buffer is up to the caller, rather than being determined by the default BUFSIZ. The setlinebuf function is exactly equivalent to the call:

     setvbuf(stream, (char *)NULL, _IOLBF, 0);

Examples:

/* this program shows setting up a buffer using setbuf * /
#include <stdio.h>
int main()
{
        FILE *fp;
        char FullBuf[100];
        char msg[100];
        char * rptr;
        char name[20] = "c:\setbuf1.txt";
        fp = fopen(name, "w+");
        if (fp == NULL)
                {
                printf ("fopen failed");
                return -1;
                }
        setbuf(fp, FullBuf);  // Fully buffered
        if (ferror(fp))
                {
                printf ("setbuf failed");
                fclose(fp);
                unlink(name);
                return -1;
                }
        fprintf(fp, "we are trying to buffer 20 characters at once ");
        
        fclose(fp);
        fp=fopen(name,"r");
        rptr = fgets(msg,100,fp);
        if(rptr == NULL)
                {
                printf("fgets failed");
                fclose(fp);
                return -1;
                }
        printf("file reading returned \"%s\",msg);
        fclose(fp);
        
        unlink(name);
        return 0;
}

Output

file reading returned "we are trying to buffer 20 characters at once"

Parameters

`__sFILE__sFILE *`
`char *`	Note: This description also covers the following functions - `setbuffer(FILE ,char ,int)setbuffer(FILE ,char ,int)` `setlinebuf(FILE )setlinebuf(FILE )` `setvbuf(FILE ,char ,int,size_t)setvbuf(FILE ,char ,int,size_t)`

Description

Parameters

`__sFILE__sFILE *`
`char *`
`int`
`size_tsize_t`	Refer to `setbuf(FILE ,char )setbuf(FILE ,char )` for the documentation

Return value

int

Description

Parameters

`char *`
`const char *`
`...`

Return value

int

Description

Parameters

`const char *`
`const char *`
`...`

Return value

int

Description

Note: This description also covers the following functions - tmpnam(char *)tmpnam(char *) tempnam(const char *,const char *)tempnam(const char *,const char *)

The tmpfile function returns a pointer to a stream associated with a file descriptor returned by the routine mkstemp . The created file is unlinked before tmpfile returns, causing the file to be automatically deleted when the last reference to it is closed. The file is opened with the access value 'w+'. The file is created in the directory determined by the environment variable TMPDIR if set. The default location if TMPDIR is not set is /tmp .

 The tmpnam function returns a pointer to a file name, in the P_tmpdir directory, which did not reference an existing file at some 
  indeterminate point in the past. P_tmpdir is defined in the include file #include <stdio.h>. If the argument str is non- NULL , the file name is copied to the buffer it references. Otherwise, 
  the file name is copied to a static buffer. In either case, tmpnam returns a pointer to the file name.

The buffer referenced by str is expected to be at least L_tmpnam bytes in length. L_tmpnam is defined in the include file #include <stdio.h>.

The tempnam function is similar to tmpnam , but provides the ability to specify the directory which will contain the temporary file and the file name prefix.

The environment variable TMPDIR (if set), the argument tmpdir (if non- NULL ), the directory P_tmpdir , and the directory /tmp are tried, in the listed order, as directories in which to store the temporary file.

The argument prefix , if non- NULL , is used to specify a file name prefix, which will be the first part of the created file name. The tempnam function allocates memory in which to store the file name; the returned pointer may be used as a subsequent argument to free .

Examples:

#include<stdio.h> //SEEK_SET, printf, tmpfile, FILE
#include<sys/stat.h> //S_IWUSR
 
int main()
{
//create the tmp directory
 mkdir("c:\tmp", S_IWUSR);
 
//call tmpfile to create a tempory file
 FILE* fp = tmpfile();
 char buf[10];
 
 if(fp)
 {
     //write onto the file
     fprintf(fp, "%s", "hello");
     fflush(fp);
  
     //seek to the beginning of the file
     fseek(fp, SEEK_SET, 0); //beg of the file
  
     //read from the file
     fscanf(fp, "%s", buf);
     fflush(fp);
 
     //close the file
     fclose(fp);
 }
 
 printf("buf read: %s", buf);
 
 return 0;
}

Output

buf read: hello

#include<stdio.h> //tmpnam, printf, FILE
#include<sys/stat.h> //S_IWUSR
#include<errno.h> //errno
  
int main()
{
 //create a directory c:\system emp
 mkdir("c:\system\temp", S_IWUSR);
  
 char buf[L_tmpnam];
 char rbuf[10];
  
 //call tmpnam() to create a file
 char *rval = tmpnam(buf);
  
 errno = 0;
 //open the file with the name returned by tmpnam()
 FILE *fp = fopen(buf, "w");
  
 if (fp == NULL)
 {
     printf("fopen of file returned by tmpnam() failed -  (*__errno())  %d ", errno);
     return -1;
 }
    
 if(fp)
 {
    fprintf(fp, "%s", "check");
    fclose(fp);
 }
   
 fp = fopen(buf, "r");
  
 if(fp)
 {
     fscanf(fp, "%s", rbuf);
     fclose(fp);
 }
  
 printf("read from file: %s", rbuf);
 printf("argument buf: %s", buf);
 printf("return value: %s", rval);
  
 return 0;
}

Output

read from file: check
argument buf: /System/temp/tmp.0.U9UPTx
return value: /System/temp/tmp.0.U9UPTx

Limitations:

The str parameter in tmpnam(char *)tmpnam(char *) respectively should not exceed 256 characters in length.
The tmpdir parameter in tempnam(const char *,const char *)tempnam(const char *,const char *) respectively should not exceed 256 characters in length.

Return value

__sFILE__sFILE *

The tmpfile function returns a pointer to an open file stream on success, and a NULL pointer on error. The tmpnam and tempfile functions return a pointer to a file name on success, and a NULL pointer on error.

Interface status:

externallyDefinedApi

IMPORT_C char* tmpnam(char *);

Description

Parameters

char *

Refer to tmpfile(void)tmpfile(void) for the documentation

Return value

char *

Interface status:

externallyDefinedApi

IMPORT_C int ungetc(int, FILE *);

Description

The ungetc function pushes the character c (converted to an unsigned char) back onto the input stream pointed to by fp . The pushed-back characters will be returned by subsequent reads on the stream (in reverse order). A successful intervening call, using the same stream, to one of the file positioning functions ( fsetpos or rewind ) will discard the pushed back characters.

One character of push-back is guaranteed, but as long as there is sufficient memory, an effectively infinite amount of pushback is allowed.

If a character is successfully pushed-back, the end-of-file indicator for the stream is cleared. The file-position indicator is decremented by each successful call to ungetc ; if its value was 0 before a call, its value is unspecified after the call.

Examples:

/* this pushing character to file stream using ungetc */
#include <stdio.h>
int main(void)
{
        int c;
        FILE* fp = fopen("c:\input.txt", "w");
        fprintf(fp, "%s", "abcdefghijklmn");
        fprintf(fp, "%c", '');
        fprintf(fp, "%s", "fdsfdsafsdabcdefghijklmn");
        fclose(fp);
        char * name = "C:\input.txt";
        fp = fopen(name, "w+");
        if (fp == NULL)
                {
                printf ("fopen failed");
                return -1;
                }
        if(ungetc('a',fp)!='a') printf("ungetc failed");
        
        fseek(fp,-1,SEEK_CUR);
        c=getc(fp);
        printf("character read from stream is \"%c\",c);
        fclose(fp);
}

Output

 character read from stream is "a"

Parameters

`int`
`__sFILE__sFILE *`

Return value

int

The ungetc function returns the character pushed-back after the conversion, or EOF if the operation fails. If the value of the argument c character equals EOF , the operation will fail and the fp will remain unchanged.

Description

Parameters

`__sFILE__sFILE *`
`const char *`
`va_list`	Refer to `printf(const char ,...)printf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`const char *`
`va_list`	Refer to `printf(const char ,...)printf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`char *`
`const char *`
`va_list`	Refer to `printf(const char ,...)printf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`char *`
`size_tsize_t`
`const char *`
`...`

Return value

int

Description

Parameters

`__sFILE__sFILE *`
`const char *`
`va_list`	Refer to `scanf(const char ,...)scanf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`const char *`
`va_list`	Refer to `scanf(const char ,...)scanf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`char *`
`size_tsize_t`
`const char *`
`va_list`	Refer to `printf(const char ,...)printf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`const char *`
`const char *`
`va_list`	Refer to `scanf(const char ,...)scanf(const char ,...)` for the documentation

Return value

int

Description

Parameters

`int`
`const char *`	Refer to `fopen(const char ,const char )fopen(const char ,const char )` for the documentation

Return value

__sFILE__sFILE *

Description

Parameters


                                 				__sFILE__sFILE *

Refer to clearerr for the documentation

Return value

int

Interface status:

externallyDefinedApi

IMPORT_C FILE* popen(const char *, const char *);

Description

The popen function opens a process by creating a pipe, forking, and invoking the shell. Since a pipe is by definition unidirectional, the type argument may specify only reading or writing, not both. The resulting stream is correspondingly read-only ("r") or write-only "w". If type is anything other than this the behavior is undefined.

The command argument is a pointer to a null-terminated string containing a shell command line. This command is passed to /bin/sh using the - c flag; interpretation, if any, is performed by the shell.

The return value from popen is a normal standard I/O stream in all respects save that it must be closed with pclose rather than fclose. Writing to such a stream writes to the standard input of the command. The command's standard output is the same as that of the process that called popen, unless this is altered by the command itself. Conversely, reading from a "popened" stream reads the command's standard output, and the command's standard input is the same as that of the process that called popen.

Note that output popen streams are fully buffered by default.

The pclose function waits for the associated process to terminate and returns the exit status of the command as returned by wait4.

Bugs:

Since the standard input of a command opened for reading shares its seek offset with the process that called popen, if the original process has done a buffered read, the command's input position may not be as expected. Similarly, the output from a command opened for writing may become intermingled with that of the original process. The latter can be avoided by calling fflush before popen. Failure to execute the shell is indistinguishable from the shell's failure to execute command, or an immediate exit of the command. The only hint is an exit status of 127. The popen function always calls sh and never calls csh.

Parameters

`const char *`
`const char *`	Note: This description also covers the following functions - `pclose(FILE *)`

Return value

__sFILE__sFILE *

The popen function returns NULL if the fork or pipe calls fail, or if it cannot allocate memory. The pclose function returns -1 if stream is not associated with a "popened" command, if stream already "pclosed" or if wait4 returns an error.

Description

Open stdin, stdout, and stderr streams and start external executable.

Parameters

`const char *file`
`const char *cmd`
`char **envp`
`int fds`

Return value

int

Interface status:

externallyDefinedApi

IMPORT_C int ftrylockfile(FILE *);

Description

Parameters


                                 				__sFILE__sFILE *

Refer to flockfile for the documentation

Return value

int

Description

These functions provide explicit application-level locking of stdio streams. They can be used to avoid output from multiple threads being interspersed, input being dispersed among multiple readers, and to avoid the overhead of locking the stream for each operation.

The flockfile function acquires an exclusive lock on the specified stream. If another thread has already locked the stream flockfile will block until the lock is released.

The ftrylockfile function is a non-blocking version of flockfile; if the lock cannot be acquired immediately ftrylockfile returns non-zero instead of blocking.

The funlockfile function releases the lock on a stream acquired by an earlier call to flockfile or ftrylockfile.

These functions behave as if there is a lock count associated with each stream. Each time flockfile is called on the stream the count is incremented and each time funlockfile is called on the stream the count is decremented. The lock is only actually released when the count reaches zero.

Examples:

#include <stdio.h>
#include <unistd.h>
#include <pthread.h> //link to the lib -libpthread
 
void* somefun(void* args)
{
FILE *fp = (FILE *)args;
printf("in thr 2");
flockfile(fp);
printf("aquired lock!");
fputc('a', fp); //fputc_unlocked() is more relevant
printf("after a from thr 2");
sleep(3);
printf("after sleep from thr 2");
fputc('b', fp);
printf("after b from thr 2");
fputc('c', fp);
printf("after c from thr 2");
funlockfile(fp);
fclose(fp);
}
int main()
{
pthread_t obj;
FILE *fp = fopen("c:\chk.txt", "w");
if(fp)
{
        flockfile(fp);
        fputc('x', fp); //fputc_unlocked() is more relevant
        printf("after x from thr 1");
        sleep(5);
        printf("after sleep from thr 1");
        pthread_create(&obj;, NULL, somefun, fp);
        printf("after calling thr 2 from thr 1");
        fputc('y', fp);
        printf("after y from thr 1");
        fputc('z', fp);
        printf("after z from thr 1");
        funlockfile(fp);
        printf("gave up lock in thr 1");
}
pthread_exit((void *)0);
}

Output

after x from thr 1
after sleep from thr 1
in thr 2
after calling thr 2 from thr 1
after y from thr 1
after z from thr 1
gave up lock in thr 1
acquired lock!
after a from thr 2
after sleep from thr 2
after b from thr 2
after c from thr 2
  
Note: The printing takes quite some time and hence the
output may not look exactly like the above one.
(try printing to the files if you are very particular)

#include <stdio.h>
#include <unistd.h>
#include <pthread.h> //link to lib -libpthread
#include <errno.h>
 
void* somefun(void* args)
{
 
FILE *fp = (FILE *)args;
 
printf("in thr 2
");
 
int i = ftrylockfile(fp);
if(i == 0)
{
        printf("aquired lock!");
        fputc('a', fp);
        printf("after a from thr 2");
        sleep(3);
        printf("after sleep from thr 2");
        fputc('b', fp);
        printf("after b from thr 2");
        fputc('c', fp);
        printf("after c from thr 2");
        funlockfile(fp);
        printf("gave up lock in thr 2");
}
else
        printf("couldn't aquire lock");
}
int main()
{
pthread_t obj;
 
FILE *fp = fopen("c:\chk.txt", "w");
 
if(fp)
{
        flockfile(fp);
        fputc('x', fp);
        printf("after x from thr 1");
        sleep(5);
        printf("after sleep from thr 1");
        pthread_create(&obj;, NULL, somefun, fp);
        printf("after calling thr 2 from thr 1");
        fputc('y', fp);
        printf("after y from thr 1");
        fputc('z', fp);
        printf("after z from thr 1");
        funlockfile(fp);
        printf("gave up lock in thr 1");
        sleep(5);
        fclose(fp);
}
pthread_exit((void *)0);
}

Output

after x from thr 1
after sleep from thr 1
in thr 2
couldn't acquire lock
after calling thr 2 from thr 1
after y from thr 1
after z from thr 1
gave up lock in thr 1
  
Note: The printing takes quite some time and hence the
output may not look exactly like the above one.
(try printing to the files if you are very particular)

Parameters


                                 				__sFILE__sFILE *

Note: This description also covers the following functions - ftrylockfile(FILE *)ftrylockfile(FILE *) funlockfile

Description

Parameters


                                 				__sFILE__sFILE *

Refer to flockfile for the documentation

Description

Parameters


                                 				__sFILE__sFILE *

Refer to fgetc(FILE *)fgetc(FILE *) for the documentation

Return value

int

Description

Refer to fgetc(FILE *)fgetc(FILE *) for the documentation

Return value

int

Description

Parameters

`int`
`__sFILE__sFILE *`	Refer to `fputc(int,FILE )fputc(int,FILE )` for the documentation

Return value

int

Description

Parameters

int

Refer to fputc(int,FILE *)fputc(int,FILE *) for the documentation

Return value

int

Description

Parameters


                                 				__sFILE__sFILE *

Refer to fgetc(FILE *)fgetc(FILE *) for the documentation

Return value

int

Description

Parameters

`int`
`__sFILE__sFILE *`	Refer to `fputc(int,FILE )fputc(int,FILE )` for the documentation

Return value

int

Description

Refer to tmpfile(void)tmpfile(void) for the documentation

Parameters

`const char *`
`const char *`

Return value

char *

Interface status:

externallyDefinedApi

IMPORT_C int asprintf(char **, const char *,...);

Description

Parameters

`char **`
`const char *`
`...`

Return value

int

Description

Parameters

`__sFILE__sFILE *`
`char *`
`int`	Refer to `setbuf(FILE ,char )setbuf(FILE ,char )` for the documentation

Description

Parameters


                                 				__sFILE__sFILE *

Refer to setbuf(FILE *,char *)setbuf(FILE *,char *) for the documentation

Return value

int

Description

Parameters

`char **`
`const char *`
`va_list`	Refer to `printf(const char ,...)printf(const char ,...)` for the documentation

Return value

int

Description

Notes: The given fd should be that of a console. If the stdio redirection server is used to redirect the stdin/stdout of a process and if the given fd maps to one of those, then the stdin will only be affected by this call. Write operations on this fd will not be affected. The earlier behavior is retained if setecho(int,uint8_t)setecho(int,uint8_t) fails.

Parameters

`int fd`
`uint8_tuint8_t echoval`	Turns On/Off the echo for the input characters. If echoval is 0, the echo is turned off and nothing gets echoed on the console. If echoval is 1, the echo is turned on. If echoval is anything else, the echo is turned off and the given printable character will be echoed instead the actual input character.

Return value

int

Upon successfull completion it returns 0, otherwise -1, setting the errno.