DrKLO/Telegram · error

%s: must name one input and one output file

Error message

%s: must name one input and one output file

What it means

Under TWO_FILE_COMMANDLINE, when no -outfile was given, jpegtran expects exactly one input and one output positional argument (file_index == argc - 2). If that invariant fails, jpegtran prints this message and calls usage() (which exits). The input is implicitly argv[file_index] and the output argv[file_index+1].

Source

Thrown at TMessagesProj/jni/mozjpeg/jpegtran.c:472

  jpeg_create_compress(&dstinfo);

  /* Scan command line to find file names.
   * It is convenient to use just one switch-parsing routine, but the switch
   * values read here are mostly ignored; we will rescan the switches after
   * opening the input file.  Also note that most of the switches affect the
   * destination JPEG object, so we parse into that and then copy over what
   * needs to affects the source too.
   */

  file_index = parse_switches(&dstinfo, argc, argv, 0, FALSE);
  jsrcerr.trace_level = jdsterr.trace_level;
  srcinfo.mem->max_memory_to_use = dstinfo.mem->max_memory_to_use;

#ifdef TWO_FILE_COMMANDLINE
  /* Must have either -outfile switch or explicit output file name */
  if (outfilename == NULL) {
    if (file_index != argc - 2) {
      fprintf(stderr, "%s: must name one input and one output file\n",
              progname);
      usage();
    }
    outfilename = argv[file_index + 1];
  } else {
    if (file_index != argc - 1) {
      fprintf(stderr, "%s: must name one input and one output file\n",
              progname);
      usage();
    }
  }
#else
  /* Unix style: expect zero or one file name */
  if (file_index < argc - 1) {
    fprintf(stderr, "%s: only one input file\n", progname);
    usage();
  }
#endif /* TWO_FILE_COMMANDLINE */

View on GitHub (pinned to 45ab8f4308)

Solutions

1. Provide exactly two positional arguments: jpegtran in.jpg out.jpg.
2. Use -outfile to name the output explicitly if positional parsing is ambiguous.
3. Quote/guard against glob expansion: pass literal filenames, not unquoted patterns.
4. Check argc in your wrapper before invoking jpegtran.

Example fix

// before
./jpegtran in.jpg
// after
./jpegtran in.jpg out.jpg

/* wrapper: ensure exactly two positional args when no -outfile */
int positional = 0, has_outfile = 0;
for (int i=1;i<argc;i++) {
  if (strncmp(argv[i],"-outfile",8)==0||strncmp(argv[i],"-o",2)==0) has_outfile=1;
  else if (argv[i][0]!='-') positional++;
}
if (!has_outfile && positional!=2) { fprintf(stderr,"need exactly INPUT OUTPUT\n"); exit(2); }

When it happens

Trigger: Invoking jpegtran with zero, one, or three+ positional file arguments and no -outfile. Examples: jpegtran in.jpg (missing output), jpegtran in.jpg out.jpg extra.jpg, or jpegtran (no files).

Common situations: Forgetting the output argument, a shell glob expanding to multiple files in the input position, a quoting bug dropping an argument, or assuming stdout output is allowed (it is not under TWO_FILE_COMMANDLINE).

Related errors

• %s: can only do one image transformation at a time
• %s: bogus -crop argument '%s'
• %s: skip region exceeds image height %d\n
• %s: crop dimensions exceed image dimensions %d x %d\n
• %s: sorry, image transformation was not compiled

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/5b4f0ef0bb6d2a91. Report an issue: GitHub.