Bash Cheat Sheet

bash --version

# Print installed Bash version.

bash -l

# Start Bash as a login shell.

bash --noprofile --norc

# Start Bash without profile or rc files.

bash -lc 'echo "$SHELL" && pwd'

# Run a command string in a login shell.

bash -n script.sh

# Parse a script without executing it.

bash -x script.sh

# Print commands as they execute.

echo $?

# Show exit status of previous command.

mkdir -p tmp && cd tmp && pwd

# Run later commands only if earlier ones succeed.

grep -q needle file.txt || echo 'not found'

# Run fallback command when previous command fails.

{ echo start; date; echo end; }

# Run a grouped list in current shell.

( cd /tmp && pwd )

# Run a grouped list in a subshell.

ps aux | grep nginx | grep -v grep

# Send output from one command to another.

set -o pipefail

# Make pipeline fail if any command fails.

echo 'hello' > out.txt

# Overwrite a file with command output.

echo 'hello' >> out.txt

# Append output to a file.

grep needle missing.txt 2> errors.log

# Write error output to a separate file.

command > all.log 2>&1

# Send both stdout and stderr to same file.

command > /dev/null 2>&1

# Silence both stdout and stderr.

cat <<'EOF'
line 1
$HOME is not expanded here
EOF

# Feed literal multiline input to a command.

grep -o '[0-9]\+' <<< 'order-123'

# Pass a short string to stdin.

while IFS= read -r line; do echo "$line"; done < input.txt

# Read a file safely without trimming backslashes.