I am trying to run a legacy Perl script on a new Ubuntu server, but I keep encountering errors. Sometimes it’s a "Permission Denied" message, and other times it triggers a "Syntax Error" near the first line. I have checked the code, and it looks correct. Could this be related to the shebang line, file encoding, or specific environment variables? What are the standard steps to debug a Perl script that won't even start?
3 answers
The "Permission Denied" error is almost always a file-level security issue. In Linux, you must explicitly mark a script as executable using chmod +x script.pl or chmod 755 script.pl. Regarding the syntax error on the first line, check your "shebang" (the #! line). If you developed the script on Windows and moved it to Linux, you likely have hidden carriage return characters (\r) at the end of your lines. These "DOS line endings" break the interpreter path. Run dos2unix script.pl to clean the file. Finally, always use perl -c script.pl to check for compilation errors without actually running the code. This is the fastest way to isolate typos or missing modules before execution.
Are you using use strict; and use warnings; at the top of your script to catch undeclared variables or suspicious code that might be causing these runtime crashes?
Check your shebang path. Use which perl in your terminal to ensure it matches the path at the very top of your script, usually #!/usr/bin/perl.
I agree with Sarah. A wrong path like #!/usr/local/bin/perl when Perl is in /usr/bin/ will throw a "Command not found" or "No such file" even if the script exists.
I haven't added those yet because I inherited this script from a previous dev. I'll add them now to see if they highlight any deeper logic issues. I suspect that a missing CPAN module might also be contributing to the failure, but the script dies so early that I'm not even getting a "Can't locate module" message yet.