What causes "%s: only one input file\n" in DrKLO/Telegram?

Pass at most one positional input and redirect stdout: djpeg in.jpg > out.ppm.

%s: only one input file\n

Error message

%s: only one input file\n

What it means

When djpeg is built WITHOUT TWO_FILE_COMMANDLINE (Unix single-file style), it accepts at most one positional input (output goes to stdout). If file_index < argc-1 there is more than one positional file, this message prints, and usage() exits.

Source

Thrown at TMessagesProj/jni/mozjpeg/djpeg.c:579

  /* 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 */

  /* Open the input file. */
  if (file_index < argc) {
    if ((input_file = fopen(argv[file_index], READ_BINARY)) == NULL) {
      fprintf(stderr, "%s: can't open %s\n", progname, argv[file_index]);
      exit(EXIT_FAILURE);
    }
  } else {
    /* default input file is stdin */
    input_file = read_stdin();
  }

  /* Open the output file. */
  if (outfilename != NULL) {
    if ((output_file = fopen(outfilename, WRITE_BINARY)) == NULL) {

View on GitHub (pinned to 45ab8f4308)

Solutions

Pass at most one positional input and redirect stdout: djpeg in.jpg > out.ppm.
If two-positional semantics are required, rebuild with TWO_FILE_COMMANDLINE defined or use -outfile.
Collapse globs/loops to a single input per invocation.

Example fix

# before: two positionals on a Unix-style build
djpeg in.jpg out.ppm
# after
djpeg in.jpg > out.ppm

Defensive patterns

Strategy: validation

Validate before calling

#!/bin/sh
pos=()
for a in "$@"; do case "$a" in -*) ;; *) pos+=("$a");; esac; done
[ "${#pos[@]}" -gt 1 ] && { echo 'this djpeg build accepts at most one input; redirect stdout for output' >&2; exit 1; }
djpeg "$@"

Type guard

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

Try / catch

if ! djpeg "$@" 2>/tmp/e; then
  grep -q 'only one input file' /tmp/e && { echo 'Unix-style build: use one input + stdout redirect'; exit 1; }
fi

Prevention

Know and document your djpeg build's commandline style.
Prefer stdout redirection (djpeg in.jpg > out.ppm) for portability.
Loop over multiple inputs instead of passing several at once.

When it happens

Trigger: Running a non-TWO_FILE_COMMANDLINE build of djpeg with two or more positional file arguments.

Common situations: Moving from a TWO_FILE_COMMANDLINE build to a Unix-style build while keeping the old two-positional invocation; shell glob producing multiple inputs; wrapper scripts that always append an output path.

Related errors

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/43b1f4dbc8d0510d. Report an issue: GitHub.