Study for reading/writing a tar file using libtar

libtar-list.c

#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <libtar.h>

int main(int argc, char *argv[]) {
  TAR *tar = NULL;
  int ret = 0;
  int exitcode = 0;

  if (argc != 2) {
    fprintf(stderr, "Usage: %s tarfile.tar\n", argv[0]);
    return 1;
  }

  ret = tar_open(&tar, argv[1], NULL, O_RDONLY, 0, 0);
  if (ret != 0) {
    fprintf(stderr, "Fail to open file: %s\n", argv[1]);
    return 1;
  }

  while (th_read(tar) == 0) {
    char *filename = th_get_pathname(tar);
    printf("%s\n", filename);
    free(filename);

    if (TH_ISREG(tar) && (tar_skip_regfile(tar) != 0)) {
      fprintf(stderr, "tar_skip_regfile()\n");
      exitcode = 2;
      break;
    }
  }

  ret = tar_close(tar);
  tar = NULL;

  return exitcode;
}

libtar-read.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <libtar.h>

int main(int argc, char *argv[]) {
  TAR *tar = NULL;
  int ret = 0;
  int th_found = 0;
  int exitcode = 0;

  if (argc != 3) {
    fprintf(stderr, "Usage: %s tarfile.tar entry\n", argv[0]);
    return 1;
  }

  ret = tar_open(&tar, argv[1], NULL, O_RDONLY, 0, 0);
  if (ret != 0) {
    fprintf(stderr, "Fail to open file: %s\n", argv[1]);
    return 1;
  }

  while (th_read(tar) == 0) {
    char *filename = th_get_pathname(tar);
    if (strcmp(filename, argv[2]) == 0) {
      th_found = 1;
      free(filename);
      break;
    }
    free(filename);

    if (TH_ISREG(tar) && (tar_skip_regfile(tar) != 0)) {
      fprintf(stderr, "tar_skip_regfile()\n");
      exitcode = 2;
      break;
    }
  }

  if (th_found == 1) {
    char buf[T_BLOCKSIZE];
    const off_t size = th_get_size(tar);
    int i;

    for (i = size; i > 0; i -= T_BLOCKSIZE) {
      int n_buf = tar_block_read(tar, buf);
      if (n_buf == EOF) {
        break;
      }

      fwrite(buf, sizeof(char), (n_buf > T_BLOCKSIZE)? T_BLOCKSIZE : n_buf, stdout);
    }

  } else if (exitcode == 0) {
    fprintf(stderr, "entry \"%s\" could not found.\n", argv[2]);
    exitcode = 1;
  }

  ret = tar_close(tar);
  tar = NULL;

  return 0;
}

libtar-write.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <libtar.h>

int main(int argc, char *argv[]) {
  TAR *tar = NULL;
  int ret = 0;
  int th_found = 0;
  int exitcode = 0;
  char tmp_filepath[] = P_tmpdir "/tartest-tmpfile-XXXXXX";
  int tmp_fd = -1;

  if (argc != 3) {
    fprintf(stderr, "Usage: %s tarfile.tar entry\n", argv[0]);
    fprintf(stderr, "       (entry body is captured from STDIN.)\n");
    return 1;
  }

  ret = tar_open(&tar, argv[1], NULL, O_RDONLY, 0, 0);
  if (ret != 0) {
    fprintf(stderr, "Fail to open file: %s\n", argv[1]);
    return 1;
  }

  while (th_read(tar) == 0) {
    char *filename = th_get_pathname(tar);
    if (strcmp(filename, argv[2]) == 0) {
      th_found = 1;
      free(filename);
      break;
    }
    free(filename);

    if (TH_ISREG(tar) && (tar_skip_regfile(tar) != 0)) {
      fprintf(stderr, "tar_skip_regfile()\n");
      exitcode = 2;
      break;
    }
  }

  tmp_fd  = mkstemp(tmp_filepath);
  if (tmp_fd == -1) {
    fprintf(stderr, "Failed to build temp file.\n");
    exitcode = 2;
  }

  if (exitcode == 0) {
    if (th_found == 1) {
      if (tar_extract_regfile(tar, tmp_filepath) != 0) {
        char *filename = th_get_pathname(tar);
        fprintf(stderr, "Failed to extract \"%s\" to \"%s\"\n", filename, tmp_filepath);
        free(filename);
        exitcode = 2;
      }
    }
  }

  ret = tar_close(tar);
  if (ret != 0) {
    perror("Failed to close tar file.");
    exitcode = 2;
  }
  tar = NULL;

  if (exitcode == 0) {
    char buf[BUFSIZ];
    ssize_t n_buf = 0;
    FILE *tmpfile = NULL;

    tmpfile = fdopen(tmp_fd, "w");
    if (tmpfile != NULL) {
      while ((n_buf = fread(buf, sizeof(char), BUFSIZ, stdin)) != 0) {
        fwrite(buf, sizeof(char), (n_buf > BUFSIZ)? BUFSIZ : n_buf, tmpfile);
      }
      fclose(tmpfile);
      tmpfile = NULL;
    } else {
      perror("Failed to open temp file.");
      exitcode = 2;
    }
  }

  if (exitcode == 0) {
    // Note: libtar is NOT able to replace a given file from an archive.
    //       So, we use GNU tar(1) command!

    const char TAR_PROG_NAME[] = "gtar"; // GNU tar. (may be tar).
    char cmdl[BUFSIZ];

    // TODO multiple file is appended when the file is already exists in the tar file.

    sprintf(cmdl, "%s -uf '%s' --xform='s|%s|%s|' -- '%s' > /dev/null 2> /dev/null",
                  TAR_PROG_NAME,
                  argv[1], // tar file
                  tmp_filepath+1, // --xform
                  argv[2],      // --xform (replacement)
                  tmp_filepath);
    // printf("%s\n", cmdl);

    // TODO do not use system() and use fork() and execve(). (Secure Coding - ENV04-C)
    system(cmdl);
  }

  if (tmp_fd != -1) {
    if (remove(tmp_filepath) == -1) {
      fprintf(stderr, "Failed to remove a temp file \"%s\".\n", tmp_filepath);
      exitcode = 2;
    }
    tmp_fd = -1;
  }

  return 0;
}