scan - Parse string using conversion specifiers in the style of sscanf
scan string format varName ?varName ...?
This command parses fields from an input string in the same fashion
as the ANSI C sscanf procedure and returns a count of the number
of conversions performed, or -1 if the end of the input string is
reached before any conversions have been performed.
String gives the input to be parsed and format indicates
how to parse it, using % conversion specifiers as in sscanf.
Each varName gives the name of a variable; when a field is
scanned from string the result is converted back into a string
and assigned to the corresponding variable.
Scan operates by scanning string and formatString together.
If the next character in formatString is a blank or tab then it
matches any number of white space characters in string (including
zero).
Otherwise, if it isn't a % character then it
must match the next character of string.
When a % is encountered in formatString, it indicates
the start of a conversion specifier.
A conversion specifier contains three fields after the %:
a *, which indicates that the converted value is to be discarded
instead of assigned to a variable; a number indicating a maximum field
width; and a conversion character.
All of these fields are optional except for the conversion character.
When scan finds a conversion specifier in formatString, it
first skips any white-space characters in string.
Then it converts the next input characters according to the
conversion specifier and stores the result in the variable given
by the next argument to scan.
The following conversion characters are supported:
- d
-
The input field must be a decimal integer.
It is read in and the value is stored in the variable as a decimal string.
- o
-
The input field must be an octal integer. It is read in and the
value is stored in the variable as a decimal string.
- x
-
The input field must be a hexadecimal integer. It is read in
and the value is stored in the variable as a decimal string.
- c
-
A single character is read in and its binary value is stored in
the variable as a decimal string.
Initial white space is not skipped in this case, so the input
field may be a white-space character.
This conversion is different from the ANSI standard in that the
input field always consists of a single character and no field
width may be specified.
- s
-
The input field consists of all the characters up to the next
white-space character; the characters are copied to the variable.
- e or f or g
-
The input field must be a floating-point number consisting
of an optional sign, a string of decimal digits possibly
containing a decimal point, and an optional exponent consisting
of an e or E followed by an optional sign and a string of
decimal digits.
It is read in and stored in the variable as a floating-point string.
- [chars]
-
The input field consists of any number of characters in
chars.
The matching string is stored in the variable.
If the first character between the brackets is a ] then
it is treated as part of chars rather than the closing
bracket for the set.
- [^chars]
-
The input field consists of any number of characters not in
chars.
The matching string is stored in the variable.
If the character immediately following the ^ is a ] then it is
treated as part of the set rather than the closing bracket for
the set.
The number of characters read from the input for a conversion is the
largest number that makes sense for that particular conversion (e.g.
as many decimal digits as possible for %d, as
many octal digits as possible for %o, and so on).
The input field for a given conversion terminates either when a
white-space character is encountered or when the maximum field
width has been reached, whichever comes first.
If a * is present in the conversion specifier
then no variable is assigned and the next scan argument is not consumed.
The behavior of the scan command is the same as the behavior of
the ANSI C sscanf procedure except for the following differences:
-
%p and %n conversion specifiers are not currently
supported.
-
For %c conversions a single character value is
converted to a decimal string, which is then assigned to the
corresponding varName;
no field width may be specified for this conversion.
-
The l, h, and L modifiers are ignored; integer
values are always converted as if there were no modifier present
and real values are always converted as if the l modifier
were present (i.e. type double is used for the internal
representation).
conversion specifier, parse, scan
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
Copyright © 1995, 1996 Roger E. Critchlow Jr.