C library - system() function

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The C stdlib library system() function is used to execute an operating system command specified by the string 'command' from a c/c++ program. It returns an integer status indicating the success or failure of the command execution.

This function is OS-dependent. We use 'system("dir")' on Windows and 'system("ls")' on Unix to list the directory contents.

Note: This function lists the files of the current directory when compiled on our system. If compiled using an online compiler, it will only show 'main main.c'.

Syntax

Following is the syntax of the system() function −

int system(const char *string)

Parameters

This function accepts a single parameter −

• string − it represents a pointer to a null-terminated string contains a command we want to execute.

Return Value

This function returns 0 if the command is executed successfully. Otherwise, it returns a non-zero value.

Example 1

In this example, we create a basic c program to demonstrate the use of system() function.

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

int main() {
   char command[50];
   
   // Set the command to "dir" (list files and directories)
   strcpy(command, "dir");
   
   //use the system fucntion to execute the command.
   system(command); 
   return 0;
}

Output

Following is the output, which shows the list of current directory −

05/10/2024  05:26 PM    <DIR>          .
05/10/2024  03:01 PM    <DIR>         ..
05/09/2024  01:57 PM               238 abort.c
05/09/2024  01:57 PM           131,176 abort.exe
05/09/2024  02:10 PM               412 abort2.c
05/09/2024  02:13 PM           131,175 abort2.exe
05/09/2024  02:23 PM               354 abort3.c
05/09/2024  02:23 PM           131,861 abort3.exe
05/09/2024  04:56 PM               399 atexit1.c
05/09/2024  04:56 PM           132,057 atexit1.exe
05/09/2024  05:30 PM               603 atexit2.c
05/09/2024  05:09 PM           132,078 atexit2.exe
05/09/2024  05:35 PM               612 atexit3.c
05/09/2024  05:35 PM           132,235 atexit3.exe
05/07/2024  11:01 AM               182 atof.cpp
05/07/2024  11:01 AM           131,175 atof.exe
.
.
.

Example 2

Let's create another c program and use the system() function to run an external command (the echo command).

#include <stdio.h>
#include <string.h>

int main() {
   char command[50];
   // Set the command to print a message
   strcpy(command, "echo Hello, World!");
   // Execute the command
   system(command); 
   return 0;
}

Output

Following is the output −

Hello, World!