perror() in C (original) (raw)

Last Updated : 3 Feb, 2025

In C, **perror() is a built-in function used to display a custom text description of the error code, which is stored in the system variable **errno.

**Example:

C `

#include <stdio.h>

int main() { FILE *fptr = fopen("gfg.text", "rw+");

  // print error 
if(fptr == NULL)
    perror("An error occurred");
return 0;

}

`

**Output

An error occurred: No such file or directory

Table of Content

• Syntax
• Examples of perror()
  • Handle Memory Allocation Error
  • Handle Insufficient Permission Error

Syntax

**clearerr() is a standard library function defined in <stdio.h> file.

perror("message");

This function does not return any value.

Examples of perror()

The following examples demonstrate the use of perror() in our C programs:

Handle Memory Allocation Error

C `

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

int main() { size_t size = 1e18; void *ptr = malloc(size);

if (ptr == NULL) {

    // Print memory allocation error using
    // perror()
    perror("Memory allocation failed");
}
else {
    free(ptr);
}
return 0;

}

`

**Output

Memory allocation failed: Cannot allocate memory

Handle Insufficient Permission Error

C `

#include <stdio.h>

int main() { FILE *file = fopen("/root/protected.txt", "w");

if (file == NULL) {
    perror("Error creating file");
    return 1;
}
fclose(file);
return 0;

}

`

**Output

Error creating file: Permission denied