Bash Scripting Loops Basics

bash-for-loop.sh

# Bash for loop
for i in /etc/*; do
  echo "${i}"
done

# Same as above (alternate syntax)
# also works with other loop structures
for i in /etc/*
do
  echo "${i}"
done

bash-while-loop.sh

# Bash while loop

# Incrementing the value
i=1

while [[ ${i} -lt 4 ]]; do
  echo "Number ${i}"
  ((i++))
done

# Decrementing the value
i=3

while [[ ${i} -gt 0 ]]; do
  echo "Number ${i}"
  ((i--))
done

bash-while-true-loop.sh

# Bash while True loop
while true; do
  # TODO
done

# Shorthand (alternate syntax)
while :; do
  # TODO
done

break-statement.sh

# Break statement
for number in $(seq 1 3); do
  if [[ ${number} == 2 ]]; then
    # Skip entire rest of
    # the loop or break out
    # the loop
    break;
  fi

  # This will only print "1"
  echo "${number}"
done

c-like-for-loop.sh

# C-like for loop
for ((i = o; i < 100; i++)); do
  echo "${i}"
done

# Same as above (alternate syntax)
# also works with other loop structures
for ((i = o; i < 100; i++))
do
  echo "${i}"
done

continue-statement.sh

# Continue statement

# Seq command can be used to generate ranges
for number in $(seq 1 3); do
  if [[ ${number} == 2 ]]; then
    continue;
  fi

  echo "${number}"
done

for-loop-ranges.sh

# For loop ranges
for i in {1..10}; do
  echo "Number: ${i}"
done

# With step size
# => {START..STOP..STEP}
for i in {5..50..5}; do
  echo "Number: ${i}"
done

reading-files.sh

# Reading files

# Using pipes
cat file.txt | while read line
do
  echo "${line}"
done

# Using input redirection
while read line; do
  echo "${line}"
done < "/path/to/file.txt"

until-or-do-loop.sh

# Until or do loop

# Incrementing
count=0

until [ ${count} -gt 10 ]; do
  echo "${count}"
  ((count++))
done

# Decrementing
count=10

until [ ${count} -eq 0 ]; do
  echo "${count}"
  ((count--))
done