perror(3p) — Linux manual page


PERROR(3P)              POSIX Programmer's Manual             PERROR(3P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       perror — write error messages to standard error

SYNOPSIS         top

       #include <stdio.h>

       void perror(const char *s);

DESCRIPTION         top

       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 POSIX.1‐2017 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.

       The perror() function shall mark for update the last data
       modification and last file status change timestamps of the file
       associated with the standard error stream 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.

       On error, perror() shall set the error indicator for the stream
       to which stderr points, and shall set errno to indicate the

       Since no value is returned, an application wishing to check for
       error situations should call clearerr(stderr) before calling
       perror(), then if ferror(stderr) returns non-zero, the value of
       errno indicates which error occurred.

RETURN VALUE         top

       The perror() function shall not return a value.

ERRORS         top

       Refer to fputc(3p).

       The following sections are informative.

EXAMPLES         top

   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 writers may prefer to use alternative interfaces
       instead of perror(), such as strerror_r() in combination with

RATIONALE         top




SEE ALSO         top

       fprintf(3p), fputc(3p), psiginfo(3p), strerror(3p)

       The Base Definitions volume of POSIX.1‐2017, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see .

IEEE/The Open Group               2017                        PERROR(3P)

Pages that refer to this page: stdio.h(0p)close(3p)psiginfo(3p)setlocale(3p)strerror(3p)