How to get the pid of another process in c?

Question

I am using the getpid and get the pid of current process. Now I am try to get the pid of other process using process name. How to get the other process pid?

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main(void)
{
    printf("My pid:%d\n", getpid());

    return 0;
}

Answer 1

1: The most common way, used by daemons. Store the pid number in a file/files. Then other processes can easily find them.

2: Portable way, spawn a child process to executes ps with a pipe. Then you can parse the text output and find your target process.

3: Non-portable way, parse the /proc/ filesystem

Often, 1 is combined with 2 or 3, in order to verify that the pid is correct.