Bash

extract filename parts

source

~% FILE="example.tar.gz"

~% echo "${FILE%%.*}"
example

~% echo "${FILE%.*}"
example.tar

~% echo "${FILE#*.}"
tar.gz

~% echo "${FILE##*.}"
gz

assign var from command output

var="$(echo "eat at joe's")"

uppercase var

echo "${var^^}"

lowercase var

echo "${var,,}"

slice var

"${VAR:offset:length}"

increment var

i=$((i+1))

native regex

if [[ "$var" =~ [0-9]{3} ]]
then
    echo 'it matches'
fi

echo "$LINENO"

clear starship error code

true

check for program

if (! type 7z > /dev/null 2>&1 )
then
    echo "7zip not installed"
fi

assign to an array

myArray=() 
myArray+=("$var")

count array elements

echo "array has ${#myArray[@]} items"

count args

echo "$#"

iterate an array

for var in "${myArray[@]}"
do
  echo "$var"
done

iterate args

for arg in "$@"
do
    echo "$arg"
done

iterate lines

while read -r line
do
    echo "$line"
done < <(echo "$lines")

substring

# ${string:offset:length}

var="hello world"
echo "${var:0:5} bob"

move to beginning and clear line

echo -ne "\r\033[2K task x% done"

date gate

if [[ "$(date '+%s')" -lt "$(date --date '2552-09-28' '+%s')" ]]
then
    echo 'skippy skippy'
    exit 0
fi

capture output and test success

if output=$(ls * 2>&1)
then
    echo "success"
else
    echo "failure"
fi

use variable in place of file

echo -n 'one\ntwo\nthree' | grep -f <(echo -e 'two\nthree\nfour')

test operators

operator desc
-eq equal to
-gt greater than
-ge greater than or equal to
-lt less than
-le less than or equal to
-f file exists
-d directory exists
-e anything exists
-x file is executable
-ef file path equals
-n string is not empty
-z string is empty

using operators

if [[ "$var" -gt 0 ]]
then
    echo "yep it's greater than zero"
fi

if test "$var" -gt 0
then
    echo "yep it's greater than zero"
fi

TODO

  • add preferred arg parsing method