What causes "Error opening input file: %s\n" in DrKLO/Telegram?

Verify the input file exists and is readable: `ls -l ` or `test -r `.

Error opening input file: %s\n

Error message

Error opening input file: %s\n

What it means

fopen(argv[argc-2], "r") on the input file returned NULL. The input file is expected to be a binary file containing length-prefixed Opus packets (4-byte big-endian length, 4-byte range-state, then payload bytes). A NULL return from fopen means the file does not exist, is not readable by the current user, or the path resolves to a directory.

Source

Thrown at TMessagesProj/jni/opus/src/repacketizer_demo.c:102

         if(merge>48)
         {
            fprintf(stderr, "-merge parameter must be less than 48.\n");
            return EXIT_FAILURE;
         }
         i++;
      } else if (strcmp(argv[i], "-split")==0)
         split = 1;
      else
      {
         fprintf(stderr, "Unknown option: %s\n", argv[i]);
         usage(argv[0]);
         return EXIT_FAILURE;
      }
   }
   fin = fopen(argv[argc-2], "r");
   if(fin==NULL)
   {
     fprintf(stderr, "Error opening input file: %s\n", argv[argc-2]);
     return EXIT_FAILURE;
   }
   fout = fopen(argv[argc-1], "w");
   if(fout==NULL)
   {
     fprintf(stderr, "Error opening output file: %s\n", argv[argc-1]);
     fclose(fin);
     return EXIT_FAILURE;
   }

   rp = opus_repacketizer_create();
   while (!eof)
   {
      int err;
      int nb_packets=merge;
      opus_repacketizer_init(rp);
      for (i=0;i<nb_packets;i++)
      {

View on GitHub (pinned to 45ab8f4308)

Solutions

Verify the input file exists and is readable: `ls -l <path>` or `test -r <path>`.
Use an absolute path to avoid working-directory ambiguity.
Quote paths containing spaces.
Check that the file-generating step (e.g., opus_demo or a custom encoder) completed successfully before invoking repacketizer_demo.

Example fix

// before
repacketizer_demo -merge 2 ./out/packets.oct /tmp/result.oct
// after
repacketizer_demo -merge 2 /abs/path/to/packets.oct /tmp/result.oct

Defensive patterns

Strategy: validation

Validate before calling

// Pre-check input file accessibility
#include <unistd.h>
if (access(argv[argc-2], R_OK) != 0) {
    fprintf(stderr, "Input file not readable: %s\n", argv[argc-2]);
    return EXIT_FAILURE;
}

Prevention

Use absolute paths for input files in scripts.
Verify file existence with `test -f` or `access()` before invoking the tool.
Check that the file-generating pipeline step succeeded.

When it happens

Trigger: Non-existent file path; permission denied (file owned by another user, no read permission); path is a directory; typo in filename; relative path resolved from the wrong working directory.

Common situations: Wrong working directory when using relative paths; file generated by a prior pipeline step that failed silently; NFS or mount issues; filename with spaces not properly quoted.

Related errors

AI-assisted analysis of DrKLO/Telegram@45ab8f4308 (2026-08-14). Data as JSON: /api/errors/9eed3715588777f4. Report an issue: GitHub.