Getting PID of process by its command name in Linux-like OS.

getpid.c

#include <dirent.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
/*
 * This is example of getting PID of process by name. Returns first matched PID or -1.
 * */
int getPidByName(const char *name)
{
	char exe_file[] = "/proc/1000000000/exe";
	char exe_path[256];
	if(NULL == name)
		return -1;
	DIR* dir = opendir("/proc");
	if(NULL == dir)
		return -1;
	struct dirent* de = 0;
	while((de = readdir(dir)) != 0)
	{
		if(strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
			continue;
		int pid = -1;
		int res = sscanf(de->d_name, "%d", &pid);
		if(res != 1)
			continue;
		snprintf(exe_file, sizeof(exe_file), "/proc/%d/exe", pid);
		ssize_t n = readlink(exe_file, exe_path, sizeof(exe_path));
		if(n == -1)
			continue;
		exe_path[n] = '\0';
		// puts(exe_path);
		if(strstr(exe_path, name) != 0)
		{
			closedir(dir);
			return pid;
		}
	}
	closedir(dir);
	return -1;
}

int main(int argc, char** argv)
{
	if(argc != 2)
	{
		printf("%s: process_name\n", argv[0]);
		exit(1);
	}
	printf("%d\n", getPidByName(argv[1]));
	return 0;
}