linux getppid能否获取指定进程id

<code class="c">#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <dirent.h>
#include <string.h>

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <pid>\n", argv[0]);
        return 1;
    }

    pid_t target_pid = atoi(argv[1]);
    char path[256];
    snprintf(path, sizeof(path), "/proc/%d/stat", target_pid);

    FILE *fp = fopen(path, "r");
    if (fp == NULL) {
        perror("fopen");
        return 1;
    }

    char buffer[1024];
    fgets(buffer, sizeof(buffer), fp);
    fclose(fp);

    char *token = strtok(buffer, " ");
    for (int i = 0; i < 3; ++i) {
        token = strtok(NULL, " ");
    }

    pid_t parent_pid = atoi(token);

    printf("Parent process ID of PID %d is %d\n", target_pid, parent_pid);
    return 0;
}</code>

<code class="bash">gcc getppid_parent.c -o getppid_parent
./getppid_parent <pid></code>