Coding⏱️ 2 min read📅 2026-05-31

How to Fix: sed fails with "unknown option to `s'" error

Error in sed command due to special character in string

Quick Answer: The issue is caused by the backslash (") in the ftp_login_template string, which is an escape character. Use a raw string literal or double backslashes to fix the error.

📋 Table of Contents

  1. ✅ Best Solutions to Fix It
  2. 🎯 Final Words

The error you're encountering is due to the presence of a single quote (') in the sed command. The issue lies in the variable expansion within your bash script. In this case, `ftp_login_template` contains a colon (:), which is not allowed in sed commands. When trying to use this template for a substitution operation, sed throws an error because it doesn't support colon-based expansions.

✅ Best Solutions to Fix It

Method 1: Quote the String

  1. Step 1: Surround your string with single quotes, like this: `sed -i -e 's/.*seb///' $ftp_dir`

Method 2: Use Parameter Expansion

  1. Step 1: Instead of directly substituting, first expand the variable and store it in a temporary file. Then use that file for the substitution operation.

🎯 Final Words

By applying these methods, you should be able to resolve the issue and successfully use your sed command. Remember to always double-check your variables for special characters before using them in bash scripts.

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