Print an error message corresponding to the value of errno

#include <stdio.h>
void perror ( const char *string  );

The perror( ) function prints a message to the standard error stream. The output includes first the string referenced by the pointer argument, if any; then a colon and a space, then the error message that corresponds to the current value of the errno variable, ending with a newline character.

Example

#define MSGLEN_MAX 256
FILE *fp;
char msgbuf[MSGLEN_MAX] = "";

if (( fp = fopen( "nonexistentfile", "r" )) == NULL )
{
  snprintf( msgbuf, MSGLEN_MAX, "%s, function %s, file %s, line %d",
            argv[0], _  _func_  _, _  _FILE_  _, _  _LINE_  _ );
  perror( msgbuf );
  return errno;
}

Assuming that there is no file available named nonexistentfile, this code results in output like the following on stderr:

./perror, function main, file perror.c, line 18: No such file or directory

See Also

strerror( )