NAME    [Toc]    [Back]

       perror - print a system error message

SYNOPSIS    [Toc]    [Back]

       #include <stdio.h>

       void perror(const char *s);

       #include <errno.h>

       const char *sys_errlist[];
       int sys_nerr;

DESCRIPTION    [Toc]    [Back]

       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  per-
       ror()  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    [Toc]    [Back]

       ANSI C, BSD 4.3, POSIX, X/OPEN

SEE ALSO    [Toc]    [Back]

       strerror(3)



				  1996-05-16			     PERROR(3)