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PERROR(3)                  Linux Programmer's Manual                 PERROR(3)

NAME
       perror - print a system error message
SYNOPSIS
       #include <stdio.h>
       void perror(const char *s);
       #include <errno.h>
       const char *sys_errlist[];
       int sys_nerr;
       int errno;
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
       sys_errlist, sys_nerr: _BSD_SOURCE
DESCRIPTION
       The  routine  perror() produces a message on the standard error output,
       describing the last error encountered during a  call  to  a  system  or
       library  function.   First  (if s is not NULL and *s is not a null byte
       ('\0')) the argument string s is printed, followed by  a  colon  and  a
       blank.  Then the message and a new-line.
       To  be  of most use, the argument string should include the name of the
       function that incurred the error.  The error number is taken  from  the
       external variable errno, which is set when errors occur but not cleared
       when successful calls are made.
       The global error list sys_errlist[] indexed by errno  can  be  used  to
       obtain the error message without the newline.  The largest message num-
       ber provided in the table is  sys_nerr-1.   Be  careful  when  directly
       accessing this list because new error values may not have been added to
       sys_errlist[].  The use of sys_errlist[] is nowadays deprecated.
       When a system call fails, it usually returns -1 and sets  the  variable
       errno  to  a  value  describing  what went wrong.  (These values can be
       found in <errno.h>.)  Many library functions do likewise.  The function
       perror()  serves to translate this error code into human-readable form.
       Note that errno is undefined after a successful library call: this call
       may  well  change  this  variable, even though it succeeds, for example
       because it internally used some other  library  function  that  failed.
       Thus,  if  a failing call is not immediately followed by a call to per-
       ror(), the value of errno should be saved.
CONFORMING TO
       The function perror() and the external errno (see errno(3)) conform  to
       C89, C99, 4.3BSD, POSIX.1-2001.  The externals sys_nerr and sys_errlist
       conform to BSD.
NOTES
       The externals sys_nerr and sys_errlist are defined  by  glibc,  but  in
       <stdio.h>.
SEE ALSO
       err(3), errno(3), error(3), strerror(3)
COLOPHON
       This  page  is  part of release 3.53 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2012-04-17                         PERROR(3)