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C program to change the permissions of file using system() function

Here, we are going to learn how to change the permissions of file using system() function using C program?
Submitted by Nidhi, on August 14, 2021

Problem statement

Given a file, we have to change the permissions of the file using the system() function by specifying the "chmod" command.

Changing the permissions of file

The system() function is a library function of <stdlib.h> or <cstdlib> header file which is used to execute the commands that can be executed in the command processor or the terminal of the operating system, and finally returns the command after it has been completed.

Syntax

int system(const char *string);

The argument string is the command to be executed.

To change the permission of a file, create (form) the command using the chmod command and pass it into the system() function.

C program to change the permissions of file

The source code to change the permissions of the file using the system() function is given below. The given program is compiled and executed using GCC compile on UBUNTU 18.04 OS successfully.

// C program to change the permissions of file
// using the system() function

#include <stdio.h>
#include <stdlib.h>
int main()
{
    char fileName[16] = "file.txt";
    char cmd[32];
    int ret = 0;

    sprintf(cmd, "chmod 666 %s", fileName);

    ret = system(cmd);
    if (ret == 0)
        printf("Permissions of file changed successfully\n");
    else
        printf("Unable to change the permissions of file\n");

    return 0;
}

Output

Permissions of file changed successfully

Explanation

Here, we created a character array fileName, which is initialized with "file.txt". Then we changed the file permissions using the system() function by specifying the "chmod" command and printed the appropriate message on the console screen.

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