A single missing space in a Bash script once cost me three hours of debugging. The worst part? The script looked fine at first glance.

Bash scripting is deceptively simple, but one small mistake can break everything. Worse, some of these issues fail silently, causing data loss, broken automation, or security risks.

This guide covers 10 Bash traps that cost people hours of frustration—and how to fix them instantly.

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1. Not Quoting Variables (Silent Failures & Data Loss)

❌ The Problem

Leaving variables unquoted leads to unexpected word splitting, which can break commands without warning.

🚨 Example of a Bug

filename="my file.txt"
rm $filename  # ❌ Tries to delete 'my' and 'file.txt' separately

✅ The Fix

rm "$filename"  # ✅ Always quote variables

🔹 Why it matters: A missing quote in a rm command can delete the wrong files—or worse, everything in a directory.

2. Using [ Instead of [[ in Conditionals

❌ The Problem

Bash has two ways to write conditionals:

• [ ... ] (old, POSIX-compliant but error-prone)
• [[ ... ]] (newer, safer)

Using [ ... ] can cause unexpected bugs with spaces, regex, and logical operators.

🚨 Example of a Bug

file="myfile.txt"
if [ -f $file ]; then  # ❌ Breaks if $file is empty or contains spaces
    echo "File exists"
fi

✅ The Fix

if [[ -f "$file" ]]; then  # ✅ Safe syntax
    echo "File exists"
fi

🔹 Why it matters: [[ ... ]] prevents syntax errors and unexpected expansions.

3. Ignoring Exit Codes ($?) and Assuming Success

❌ The Problem

Bash does not stop execution on errors unless explicitly told to.

🚨 Example of a Bug

cp important_file /backup
echo "Backup complete"  # ❌ This prints even if `cp` fails

✅ The Fix

Use set -e to exit immediately on failure:

set -e
cp important_file /backup
echo "Backup complete"  # ✅ Runs only if `cp` succeeds

🔹 Alternative Fix: Manually check exit codes:

if cp important_file /backup; then
    echo "Backup successful"
else
    echo "Backup failed"
fi

🔹 Why it matters: Prevents silent failures that corrupt automation workflows.

4. Hardcoding /bin/bash Instead of #!/usr/bin/env bash

❌ The Problem

Not all systems have Bash at /bin/bash, leading to "command not found" errors.

🚨 Example of a Bug

#!/bin/bash
echo "Hello"

Fails if Bash is in /usr/local/bin/bash.

✅ The Fix

#!/usr/bin/env bash
echo "Hello"

🔹 Why it matters: This finds Bash dynamically, ensuring compatibility across Linux distros.

5. Using cat file | grep Instead of Just grep

❌ The Problem

Useless use of cat slows down processing.

🚨 Example of a Bug

cat file.txt | grep "error"  # ❌ Unnecessary `cat`

✅ The Fix

grep "error" file.txt  # ✅ More efficient

🔹 Why it matters: Speeds up command execution, especially in loops.

6. Running Scripts Without chmod +x

❌ The Problem

If a script lacks execute permissions, running ./script.sh fails.

✅ The Fix

chmod +x script.sh

Or run explicitly with Bash:

bash script.sh

🔹 Why it matters: Prevents "Permission denied" errors when running scripts.

7. Using find -exec Instead of xargs (Performance Issue)

❌ The Problem

Using find -exec spawns a new process for every file, slowing down execution.

🚨 Example of a Bug

find . -name "*.log" -exec rm {} \;  # ❌ Runs `rm` separately for each file

✅ The Fix

find . -name "*.log" | xargs rm  # ✅ Much faster

🔹 Alternative: Use -exec ... + (if supported):

find . -name "*.log" -exec rm {} +

🔹 Why it matters: Massively improves script performance.

8. Overwriting Files Without Warning (> Instead of >>)

❌ The Problem

Using > overwrites files without a prompt.

🚨 Example of a Bug

echo "New data" > important.txt  # ❌ Overwrites existing content

✅ The Fix

Use append (>>) or safe redirection (>|):

echo "New data" >> important.txt  # ✅ Appends instead of overwriting

🔹 Extra Safety: Enable no-clobber mode:

set -o noclobber

🔹 Why it matters: Prevents accidental data loss.

9. Using echo for Command Output Instead of printf

❌ The Problem

echo does not always handle special characters and escape sequences correctly.

🚨 Example of a Bug

echo "Column1\tColumn2"

This may not print a tab correctly in some shells.

✅ The Fix

printf "Column1\tColumn2\n"

🔹 Why it matters: printf ensures consistent output formatting.

10. Using == Instead of = in sh Scripts

❌ The Problem

Bash supports ==, but POSIX sh only supports =.

🚨 Example of a Bug

#!/bin/sh
if [ "$var" == "hello" ]; then  # ❌ Works in Bash, fails in POSIX sh
    echo "Match"
fi

✅ The Fix

if [ "$var" = "hello" ]; then  # ✅ Compatible with both Bash and sh
    echo "Match"
fi

🔹 Why it matters: Ensures portability across different shells.

Final Thoughts: Debug Bash Like a Pro

Fixing these 10 common Bash mistakes will save hours of debugging.

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What’s the worst Bash mistake you’ve ever made? Drop a comment below!