Bash Cheatsheet

Bash is the command-line shell found on most Linux and macOS systems. This cheatsheet covers everyday commands and scripting basics.

Navigation

Move around the filesystem.

pwd                 # print current directory
ls -la              # list all, long format
cd /path/to/dir     # change directory
cd ..               # up one level
cd ~                # home directory

File Operations

Create, copy, move, delete.

touch file.txt      # create empty file
mkdir -p a/b/c      # create nested dirs
cp src dest         # copy
mv old new          # move / rename
rm file.txt         # delete file
rm -rf dir          # delete dir recursively

Viewing Files

Read and search content.

cat file.txt        # print file
less file.txt       # scroll file
head -n 20 file     # first 20 lines
tail -f log.txt     # follow a log
grep "error" file   # search text

Pipes & Redirection

Chain commands together.

ls | grep ".js"          # pipe output
command > out.txt        # overwrite file
command >> out.txt       # append to file
command 2> err.txt       # redirect errors
cat file | wc -l         # count lines

Variables

Store and use values.

name="Ada"
echo "Hello $name"
export PATH="$PATH:/new/bin"
count=$(ls | wc -l)

Conditionals

Branch on conditions.

if [ -f file.txt ]; then
  echo "exists"
elif [ -d dir ]; then
  echo "is dir"
else
  echo "missing"
fi

Loops

Iterate over items.

for f in *.txt; do
  echo "$f"
done

while read line; do
  echo "$line"
done < file.txt

Permissions & Processes

Manage access and running tasks.

chmod +x script.sh      # make executable
chmod 644 file          # rw-r--r--
ps aux | grep node      # find process
kill -9 <pid>           # force kill

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Bash is a powerful tool for automation and system tasks. Master these commands, then write scripts to automate repetitive workflows.

For full documentation, see https://www.gnu.org/software/bash/manual/