Bash Cheat Sheet

name="John"

echo $name
echo ${name}

read -p "Enter name: " name

fruits=("apple" "banana" "cherry")

echo ${fruits[0]}
echo ${fruits[@]}

echo ${#name}  # String length
echo ${#fruits[@]}  # Array length

if [ $x -gt 0 ]; then
  echo "positive"
elif [ $x -lt 0 ]; then
  echo "negative"
else
  echo "zero"
fi

for i in 1 2 3 4 5; do
  echo $i
done

for i in {1..5}; do
  echo $i
done

while [ $count -lt 10 ]; do
  ((count++))
done

case $day in
  "Mon") echo "Monday" ;;
  "Tue") echo "Tuesday" ;;
  *) echo "Other" ;;
esac

-eq  # Equal
-ne  # Not equal
-gt  # Greater than
-lt  # Less than
-ge  # Greater or equal
-le  # Less or equal

=   # Equal
!=  # Not equal
-z  # Empty
-n  # Not empty

-f  # Is file
-d  # Is directory
-e  # Exists
-r  # Readable
-w  # Writable
-x  # Executable

greet() {
  echo "Hello, $1!"
}

greet "World"

add() {
  echo $(($1 + $2))
}
result=$(add 5 3)

myfunc() {
  local name="John"
}

full="$first $last"

echo ${name:0:5}  # First 5 chars

echo ${name/old/new}  # First occurrence
echo ${name//old/new}  # All occurrences

echo ${name^^}

echo ${name,,}

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

echo "text" > file.txt   # Overwrite
echo "text" >> file.txt  # Append

if [ -f "file.txt" ]; then
  echo "File exists"
fi

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

cat file.txt | grep "pattern"

command > output.txt 2>&1

today=$(date +%Y-%m-%d)

if [ $? -eq 0 ]; then
  echo "Success"
fi