Difference between "system" and "exec" in Linux?

c linux exec fork
Kamil picture Kamil · Nov 8, 2009 · Viewed 80.9k times · Source

What is the difference between system and exec family commands? Especially I want to know which one of them creates child process to work?

Answer

Carl Norum picture Carl Norum · Nov 8, 2009

system() calls out to sh to handle your command line, so you can get wildcard expansion, etc. exec() and its friends replace the current process image with a new process image.

With system(), your program continues running and you get back some status about the external command you called. With exec(), your process is obliterated.

In general, I guess you could think of system() as a higher-level interface. You could duplicate its functionality yourself using some combination fork(), exec(), and wait().

To answer your final question, system() causes a child process to be created, and the exec() family do not. You would need to use fork() for that.

Related questions

how to set close-on-exec by default

I'm implementing a library to run commands. The library is C, on Linux. It currently does a popen() call to run a command and get output. The problem is that the command inherits all currently open file handlers. If I …

Read More
I do not understand how execlp() works in Linux

I have spent the last 2 days trying to understand the execlp() system call, but yet here I am. Let me get straight to the issue. The man page of execlp declares the system call as int execlp(const char *file, …

Read More
In C how do you redirect stdin/stdout/stderr to files when making an execvp() or similar call?

I have the following code: pid_t pid = fork(); if (pid == -1) { // ... } else if (pid == 0) { stdin = someopenfile; stdout = someotherfile; stderr = somethirdopenfile; execvp(args[0], args); // handle error ... } else { // ... } The problem is, the input/output of the execvp() call is still the …

Read More