Useful bash script

!bash scripts

This gist contains useful bash scripts

bash array check

containsElement () {
  local _flag="false"
  local match="$1"
  shift
  for item; do [[ "$item" == "$match" ]] && _flag="true"; done
  echo ${_flag}
}

array=("something to search for" "a string" "test2000")
_found=$(containsElement "a string" "${array[@]}")
if [[ ${_found} == "true" ]]; then
  echo "found"
else
  echo "not found"
fi

bash create archieve

mkdir hello_world
mkdir hello_world/dir1
mkdir hello_world/dir2

tar --create --remove-files hello_world | gzip > hello_world.tar.gz
[tar --create --remove-files __FOLDER__NAME__ | gzip > __FILE__NAME__.tar.gz]

tar -czf hello_world.tar.gz --remove-files hello_world
[tar -czf __FILE__NAME__.tar.gz --remove-files __FOLDER__NAME__]

tar -xzf hello_world.tar.gz; rm -rf hello_world.tar.gz

check occurrences of space or tab

https://unix.stackexchange.com/questions/22273/how-to-use-regex-as-field-separator-in-awk

# ignores heading and checks for number of \t in each line
awk 'NR!=1' test.txt | awk -F '\t' '{ print NF-1 }'

# doesn't ignore heading
awk -F '\t' '{ print NF-1 }' test.txt

# ignores heading and checks for number of all kind of spaces in each line
awk 'NR!=1' test.txt | awk -F '[[:space:]]*' '{ print NF-1 }'

$ cat test.txt
this is heading
hello world space       one     two     three           five

create passwordless ssh from one machine to another machine

# in machine1
$ ssh-keygen -t rsa
> generates: id_rsa, id_rsa.pub

# copy the id_rsa.pub from the machine1 to the machine2 via a jumphost or an intermediary machine

# in machine2
$ mkdir /root/.ssh (in case if .ssh is not present)
$ chmod 700 /root/.ssh (in case if .ssh is not present)
$ cat /root/.ssh/id_rsa.pub >> /root/.ssh/authorized_keys
$ chmod 640 /root/.ssh/authorized_keys

This does passwordless access from machine1 -> machine2. If need to do the other way around then follow the same other way around.

trap function

$ touch call.sh
#!/usr/bin/env bash

set -E

_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

source "${_dir}/main.sh"

_file="${_dir}/$(basename "${BASH_SOURCE[0]}")"
_base="$(basename "${_file}" .sh)"

trap "cleanup ${_base}" ERR

just_run_something "message this"

touch main.sh
#!/usr/bin/env bash

function cleanup() {
   local _BASE="$1"

   echo "_BASE: ${_BASE}"

   echo "Caught Signal ... cleaning up."
   rm -rf /tmp/created
   echo "Done cleanup ... quitting."
}


function just_run_something {
   echo "$1"
   # touch /root/created # fail things
   touch /tmp/created
}