Question

I’ve tried several times to write a function to remove directories and the files within the directories, like rm -r, but I haven’t managed to do it. The technique I’ve tried is:

/* rm command */
#include <fts.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#define DEBUG

int rm_file(const char **argv);
int rm_tree(const char **argv);
void usage(void);

int rflag = 0;

int main(int argc, char *argv[])
{
    int ch;

    while((ch = getopt(argc, argv, "Rr")) != -1) {
        switch(ch) {
            case 'R':
            case 'r':
                rflag = 1;
                break;
            default:
                usage();
        }
    }
    argc -= optind;
    argv += optind;

    while(*argv) {
        if(rflag)
            rm_tree(argv);
        else
            rm_file(argv);
        argv++;
    }

    return 0;
}

int rm_tree(const char **argv)
{
    FTS *ftsp;
    FTSENT *ftsent;

    if((ftsp = fts_open(argv, 0, NULL)) == NULL) {
        fprintf(stderr, "error: rm: can't stat directory\n");
        return 1;
    }

    while((ftsent = fts_read(ftsp)) != NULL) {
        switch(ftsent->fts_info) {
            case FTS_DNR:
                fprintf(stderr, "error: rm: can't stat directory\n");
                break;
#ifndef DEBUG
            case FTS_D:
                rm_tree(&ftsent->fts_accpath);
                break;
#endif
            case FTS_F:
                if(unlink(ftsent->fts_accpath) == -1) {
                    fprintf(stderr, "error: rm: can't remove file\n");
                }
                break;
            case FTS_SL:
                if(unlink(ftsent->fts_accpath) == -1) {
                    fprintf(stderr, "error: rm: can't remove file\n");
                }
                break;
            default:
                if(unlink(ftsent->fts_accpath) == -1) {
                    fprintf(stderr, "error: rm: can't remove file\n");
                }
                break;
        }
    }

    if(rmdir(*argv) == -1) {
        fprintf(stderr, "error: rm: can't remove directory\n");
        return 1;
    }

    return 0;
}

int rm_file(const char **argv)
{
    struct stat st;

    if(lstat(*argv, &st) == -1) {
        fprintf(stderr, "error: rm: can't stat file\n");
        return 1;
    }

    if(S_ISDIR(st.st_mode)) {
        fprintf(stderr, "error: rm: can't remove directory\n");
        return 1;
    }

    if(unlink(*argv) == -1) {
        fprintf(stderr, "error: rm: can't remove file\n");
        return 1;
    }

    return 0;
}

void usage(void) 
{
    fprintf(stderr, "usage: rm file1 file2\n");
    exit(1);
}

But invariably, I get a segmentation fault or it just doesn’t work. Am I looking in the right direction? I’ve tried using the ftw() functions and the opendir() functions, but I just haven’t been able to figure out how to get this to work. I would appreciate it if someone could help.

The code included in the debug tags is where it tends to fail.

Answer 1

Take a look at how it is done in practice by analysing source code of rm in open source operating systems, e.g. OpenBSD (look for rm_tree).