running shell script using c programming

Question

hello every one I want to ask that I am making a program in which i have to run shell script using c program. up till now i have separated the arguments. and i have searched that exec should be use to run shell scripts but i am totally confused as there are many variants of exec and by reading the man pages i am unable to find which is best suitable

Also in some exec function first arg is

path

and some have

pointer to file

what is the difference and what should i write in place of it.kindly guide me thanks

Answer 1

Running a shell script from a C program is usually done using

#include <stdlib.h>
int system (char *s);

where s is a pointer to the pathname of the script, e.g.

int rc = system ("/home/username/bin/somescript.sh");

If you need the stdout of the script, look at the popen man page.

Answer 2

All exec* library functions are ultimately convenience wrappers over the execve() system call. Just use the one that you find more convenient.

The ones that end in p (execlp(), execvp()) use the $PATH environment variable to find the program to run. For the others you need to use the full path as the first argument.

The ones ending in e (execle(), execve()) allow you to define the environment (using the last argument). This way you avoid potential problems with $PATH, $IFS and other dangerous environment variables.

The ones wih an v in its name take an array to specify arguments to the program to run, while the ones with an l take the arguments to the program to run as variable arguments, ending in (char *)NULL. As an example, execle() is very convenient to construct a fixed invocation, while execv* allow for a number of arguments that varies programatically.

Answer 3

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

#define SHELLSCRIPT "\
for ((i=0 ; i < 10 ; i++))\n\
do\n\
echo \"Count: $i\"\n\
done\n\
"

int main(void)
{
  puts("Will execute sh with the following script:");
  puts(SHELLSCRIPT);
  puts("Starting now:");
  system(SHELLSCRIPT);
  return 0;
}

Reference: http://www.unix.com/programming/216190-putting-bash-script-c-program.html