linux常用命令源代码

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

int main(int argc, char *argv[]) {
    DIR *dir;
    struct dirent *entry;

    dir = opendir(".");
    if (dir == NULL) {
        perror("opendir");
        return 1;
    }

    while ((entry = readdir(dir)) != NULL) {
        printf("%s
", entry->d_name);
    }

    closedir(dir);
    return 0;
}

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    int fd;
    char buffer[1024];

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <filename>
", argv[0]);
        return 1;
    }

    fd = open(argv[1], O_RDONLY);
    if (fd == -1) {
        perror("open");
        return 1;
    }

    while (read(fd, buffer, sizeof(buffer)) > 0) {
        write(STDOUT_FILENO, buffer, sizeof(buffer));
    }

    close(fd);
    return 0;
}

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

int main(int argc, char *argv[]) {
    FILE *file;
    char line[1024];

    if (argc != 3) {
        fprintf(stderr, "Usage: %s <pattern> <filename>
", argv[0]);
        return 1;
    }

    file = fopen(argv[2], "r");
    if (file == NULL) {
        perror("fopen");
        return 1;
    }

    while (fgets(line, sizeof(line), file)) {
        if (strstr(line, argv[1])) {
            printf("%s", line);
        }
    }

    fclose(file);
    return 0;
}