perror

Writes a short error message to stderr describing the current value of errno.

Format

#include  <stdio.h>

void perror  (const char *str);

Argument

str: Usually the name of the program that caused the error.

Description

This function uses the error number in the external variable errno to retrieve the appropriate locale-dependent error message. The function writes out the message as follows: str (a user-supplied prefix to the error message), followed by a colon and a space, followed by the message itself, followed by a new-line character.

See the description of errno in Chapter 4 for a list of possible errors.

Example

#include <stdio.h>
#include <stdlib.h>

main(argc,argv)
int argc;
char *argv[];
{
 FILE *fp;
 int status;
 int total_recs = -1;

 fp = fopen(argv[1],"r");                   /* Open an input file. */
 if (fp == NULL)
  {

  /*
   * If the fopen call failed, perror prints out a diagnostic:
   *
   *    "open: <error message>"
   *    This error message provides a diagnostic explaining
   *    the cause of the failure.
   *
   */
  perror("open");
  exit(1);
  }
 }

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