What causes "%s: must name one input and one output file " in DrKLO/Telegram?

Provide exactly one input and one output file positionally when not using -outfile, e.g. cjpeg in.ppm out.jpg.

%s: must name one input and one output file

Error message

%s: must name one input and one output file

What it means

In TWO_FILE_COMMANDLINE mode, when no -outfile switch was given, cjpeg expects exactly two positional file arguments (input and output). If file_index (the count of non-switch positionals after parsing) is not argc-2, the count is wrong and this message prints, then usage() exits. This branch covers the missing-output-file case.

Source

Thrown at TMessagesProj/jni/mozjpeg/cjpeg.c:718

   */

  cinfo.in_color_space = JCS_RGB; /* arbitrary guess */
  jpeg_set_defaults(&cinfo);

  /* Scan command line to find file names.
   * It is convenient to use just one switch-parsing routine, but the switch
   * values read here are ignored; we will rescan the switches after opening
   * the input file.
   */

  file_index = parse_switches(&cinfo, argc, argv, 0, FALSE);

#ifdef TWO_FILE_COMMANDLINE
  if (!memdst) {
    /* 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();
  }

View on GitHub (pinned to 45ab8f4308)

Solutions

Provide exactly one input and one output file positionally when not using -outfile, e.g. cjpeg in.ppm out.jpg.
Alternatively use -outfile <path> and pass a single input positional.
If you need stdout output, use a build without TWO_FILE_COMMANDLINE or redirect the single output to /dev/stdout.

Example fix

# before: only input given, no output
cjpeg in.ppm
# after
cjpeg in.ppm out.jpg
# or
cjpeg -outfile out.jpg in.ppm

Defensive patterns

Strategy: validation

Validate before calling

#!/bin/sh
# Ensure exactly two positionals when no -outfile is present (TWO_FILE_COMMANDLINE build)
has_outfile=0; pos=()
for a in "$@"; do case "$a" in -outfile) has_outfile=1;; -*) ;; *) pos+=("$a");; esac; done
[ "$has_outfile" -eq 0 ] && [ "${#pos[@]}" -ne 2 ] && { echo 'need exactly one input and one output file' >&2; exit 1; }
cjpeg "$@"

Type guard

// n/a: argv-count validation in the caller.

Try / catch

if ! cjpeg "$@" 2>/tmp/e; then
  grep -q 'must name one input and one output file' /tmp/e && { echo 'supply input + output (or use -outfile)'; exit 1; }
fi

Prevention

In wrapper scripts, separate options from positionals explicitly and assert the positional count before exec.
Default to -outfile for explicit output to avoid ambiguity.
Document which build flavor (TWO_FILE_COMMANDLINE) is deployed.

When it happens

Trigger: Calling cjpeg with no -outfile and not exactly two positional arguments: zero, one, or three+ positional file names (e.g. only an input file, or input plus multiple outputs).

Common situations: Expecting cjpeg to write to stdout when TWO_FILE_COMMANDLINE is defined (it does not in this mode); forgetting the output argument; shell glob expanding to many files; piping assumptions.

Related errors

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/75a5a414a4de30bf. Report an issue: GitHub.