NAME

perror - write error messages to standard error

SYNOPSIS

#include <stdio.h>

void perror(const char *s);


DESCRIPTION

^[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

The perror() function shall map the error number accessed through the symbol errno to a language-dependent error message, which shall be written to the standard error stream as follows:

• First (if s is not a null pointer and the character pointed to by s is not the null byte), the string pointed to by s followed by a colon and a <space>.

• Then an error message string followed by a <newline>.

The contents of the error message strings shall be the same as those returned by strerror() with argument errno.

^[CX] The perror() function shall mark the file associated with the standard error stream as having been written (st_ctime, st_mtime marked for update) at some time between its successful completion and exit(), abort(), or the completion of fflush() or fclose() on stderr.

The perror() function shall not change the orientation of the standard error stream.

RETURN VALUE

The perror() function shall not return a value.

ERRORS

No errors are defined.

EXAMPLES

Printing an Error Message for a Function

The following example replaces bufptr with a buffer that is the necessary size. If an error occurs, the perror() function prints a message and the program exits.

#include <stdio.h>
#include <stdlib.h>
...
char *bufptr;
size_t szbuf;
...
if ((bufptr = malloc(szbuf)) == NULL) {
    perror("malloc"); exit(2);
}
...

APPLICATION USAGE

None.

RATIONALE

None.

FUTURE DIRECTIONS

None.

SEE ALSO

strerror() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 5

A paragraph is added to the DESCRIPTION indicating that perror() does not change the orientation of the standard error stream.

Issue 6

Extensions beyond the ISO C standard are marked.