Linux获取进程pid

-/proc是系统中当前运行的所有进程的对应目录，以进程的 PID号为目录名，可用来获取进程信息。
-/proc/pid/comm是对应pid号的进程名。

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

int main(int argc, char* argv[]){
    if(argc < 2){
        printf("expected proc name\nusage:\t%s [proc name]\n",argv[0]);
        return -1;
    }
    if(strcmp(argv[1],"--help") == 0){
        printf("usage:\t%s [proc name]\n",argv[0]);
        return 0;
    }

    #define READ_BUF_SIZE 64
    DIR* dir;
    struct dirent* next;
    FILE* status;
    char file_name[READ_BUF_SIZE];
    char proc_name[READ_BUF_SIZE];
    dir = opendir("/proc");
    if(!dir){
        printf("open error /proc\n");
        return -1;
    }
    while((next = readdir(dir)) != NULL){
        if(!isdigit(*next->d_name))
            continue;

        memset(file_name,0,READ_BUF_SIZE);
        memset(proc_name,0,READ_BUF_SIZE);
        sprintf(file_name,"/proc/%s/comm",next->d_name);
        if(!(status = fopen(file_name,"r"))){
            printf("open error %s",file_name);
            continue;
        }
        fscanf(status, "%s",proc_name);
        if(strcmp(argv[1],proc_name) == 0){
            printf("%d\n",atoi(next->d_name));
            fclose(status);
            return atoi(next->d_name);
        }
    }
    fclose(status);
    return 0;
}