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Literal carriage return. Run script through tr -d '\r' .

Problematic code:

$ cat -v myscript
#!/bin/sh^M
echo "Hello World"^M

Correct code:

$ cat -v myscript
#!/bin/sh
echo "Hello World"

Rationale:

The script uses Windows/MS-DOS style \r\n line terminators instead of Unix-style \n terminators. The additional \r aka ^M aka carriage return characters will be treated literally, and results in all sorts strange bugs and messages.

You can verify this with cat -v yourfile and see whether or not each line ends with a ^M. To delete them, open the file in your editor and save the file as "Unix", "Unix/macOS Format", :set ff=unix or similar if it supports it.

If you don't know how to get your editor to save a file with Unix line terminators, you can use tr:

tr -d '\r' < badscript > goodscript
# or
dos2unix badscript

This will read a script badscript with possible carriage returns, and write goodscript without them.

Exceptions:

None

Related resources:

• BashFaq: How do I convert a file from MS-DOS format to Unix format (remove CRs from CR-LF line terminators)?
• StackOverflow: Are shell-scripts sensitive to encoding and line-endings?

ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.