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;

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.  The argument string s is printed first,  then
       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 non-erroneous 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 number 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[].

       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 perror, the value of errno should be saved.

CONFORMING TO

       ANSI C, BSD 4.3, POSIX, X/OPEN

SEE ALSO

       strerror(3)

                                                   May 16 1996                                         PERROR(3)