List of handful bash commands

bash-commands.sh

#!/bin/bash

# signals bash to stop execution on any fail
set -e

# if variable not defined
if [[ -z "$BACKUP_FILE" ]]; then
  ...
fi

# if variable defined
if [[ -n "$BACKUP_FILE" ]]; then
  ...
fi

# increment number into a variable
DAYS_TO_KEEP=$(($DAYS_TO_KEEP + 1))

# split whitespaces into break lines
echo "1 2 3 4 5" | tr " " "\n"
echo "1 2 3 4 5" | tr '[[:space:]]' '\n'

# get item from xargs
ls . | xargs -I {} echo File {}

# get result after row 10
ls | awk "NR>10"

# count words
cat myfile | wc -w

# count rows
cat myfile | wc -l

# for loop
for FILE in $FILES; do
  echo ">FILE: $FILE"
done

# set variable with multiline text
# To understand the "| true" below:
# https://stackoverflow.com/questions/15429330/how-to-specify-a-multi-line-shell-variable/15429426#comment21828145_15429426
read -d '' SCRIPT <<EOF || true
ls
pwd
echo "Teste"
EOF

# convert break lines in ";"
SCRIPT=$(echo "$SCRIPT" | tr '\n' ';')

# read a variable from host machine when executing a lftp command in remote server
lftp \
  -u "user,pwd" \
  -e "set ftp:ssl-allow no; cd /data/; rm $(echo $FILES); quit" \
  "my-remote-server"
  
# find content in files ignoring path
grep --exclude-dir="<ignore-path>" '<term>' -R .

# loop find results
for file in $(find "<path>"); do
  echo file
done

# check type exist
type_exists() {
    if [ $(type -P $1) ]; then
      return 0
    fi
    return 1
}

if ! ( type_exists "gnome-shell" ) ; then
  echo "Does not exist"
fi