linux access函数

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

int main() {
    if (access("example.txt", F_OK) != -1) {
        printf("File exists.\n");
    } else {
        perror("File does not exist");
    }

    if (access("example.txt", R_OK) != -1) {
        printf("File is readable.\n");
    } else {
        perror("File is not readable");
    }

    if (access("example.txt", W_OK) != -1) {
        printf("File is writable.\n");
    } else {
        perror("File is not writable");
    }

    if (access("example.txt", X_OK) != -1) {
        printf("File is executable.\n");
    } else {
        perror("File is not executable");
    }

    return 0;
}

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

int main() {
    if (access("nonexistent.txt", F_OK) != -1) {
        printf("File exists.\n");
    } else {
        perror("File does not exist");
        printf("Error: %s\n", strerror(errno));
    }
    return 0;
}