How can I execute a Bash program from C? [duplicate] - c

Question

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Is it possible to include a shell script in a C program
(1 answer)
Closed 6 years ago.
How can I execute a command with bash? system() uses sh and not bash.
I know that I can execute commands in bash with system("/bin/bash -c command"). But I have a very long command and /bin/bash -c gives me problems. What I need is bashrun(command) or something else.
The command is a string, not a file

Answer 1

Case1 : script from a file - Use the shebang
#!/usr/bin/env bash
at the top of your script and then do
int status=system("/full/path/to/script");
if(status==-1){
// failure mode
}
Case2 : script stored as a string
Do something like below
char *command="$(which bash) -c 'ls'";
int status=system(command);
if (status==-1){
//failure mode
}

Answer 2

If you're creating a very long shell command and you need bash to interpret it, then you have two real options:
Save the text into a file and invoke bash with the filename as a single argument (equivalently, use a shebang in the file to specify bash as the interpreter, make the file executable, and invoke that as command), or
Start an instance of bash with popen() and write the shell command as standard input to the bash process.
If you're having problems due to shell script quoting (rather than the command length), then either of those options would work, or you could implement the equivalent of system() but using execl() to pass the argument without going through sh. I'm assuming a POSIX-type system here.
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
int run_bash(const char *command)
{
int pid = fork();
if (pid < 0) {
/* failed */
perror("fork");
return pid;
} else if (pid == 0) {
/* child */
execl("/bin/bash", "bash", "-c", command, (char*)NULL);
perror("exec");
exit(EXIT_FAILURE);
} else {
/* parent */
int status;
do {
waitpid(pid, &status, 0);
} while (!WIFEXITED(status));
return WEXITSTATUS(status);
}
}
int main(void)
{
run_bash("echo '*'");
}