NAME
openpam_readword —
read a word from a
file, respecting shell quoting rules
SYNOPSIS
#include <sys/types.h>
#include <stdio.h>
#include <security/pam_appl.h>
#include <security/openpam.h>
char *
openpam_readword(
FILE
*f,
int *lineno,
size_t *lenp);
DESCRIPTION
The
openpam_readword() function reads the next word from a
file, and returns it in a NUL-terminated buffer allocated with
malloc(3).
A word is a sequence of non-whitespace characters. However, whitespace
characters can be included in a word if quoted or escaped according to the
following rules:
- An unescaped single or double quote introduces a quoted
string, which ends when the same quote character is encountered a second
time. The quotes themselves are stripped.
- Within a single- or double-quoted string, all whitespace
characters, including the newline character, are preserved as-is.
- Outside a quoted string, a backslash escapes the next
character, which is preserved as-is, unless that character is a newline,
in which case it is discarded and reading continues at the beginning of
the next line as if the backslash and newline had not been there. In all
cases, the backslash itself is discarded.
- Within a single-quoted string, double quotes and
backslashes are preserved as-is.
- Within a double-quoted string, a single quote is
preserved as-is, and a backslash is preserved as-is unless used to escape
a double quote.
In addition, if the first non-whitespace character on the line is a hash
character (#), the rest of the line is discarded. If a hash character occurs
within a word, however, it is preserved as-is. A backslash at the end of a
comment does cause line continuation.
If
lineno is not
NULL
, the integer
variable it points to is incremented every time a quoted or escaped newline
character is read.
If
lenp is not
NULL
, the length of
the word (after quotes and backslashes have been removed) is stored in the
variable it points to.
RETURN VALUES
If successful, the
openpam_readword() function returns a
pointer to a dynamically allocated NUL-terminated string containing the first
word encountered on the line.
The caller is responsible for releasing the returned buffer by passing it to
free(3).
If
openpam_readword() reaches the end of the line or file
before any characters are copied to the word, it returns
NULL
. In the former case, the newline is pushed back
to the file.
If
openpam_readword() reaches the end of the file while a
quote or backslash escape is in effect, it sets
errno to
EINVAL
and returns
NULL
.
IMPLEMENTATION NOTES
The parsing rules are intended to be equivalent to the normal POSIX shell
quoting rules. Any discrepancy is a bug and should be reported to the author
along with sample input that can be used to reproduce the error.
SEE ALSO
openpam_readline(3),
openpam_readlinev(3),
pam(3)
STANDARDS
The
openpam_readword() function is an OpenPAM extension.
AUTHORS
The
openpam_readword() function and this manual page were
developed by
Dag-Erling Smørgrav
<
des@des.no>.