Bash

Brief

ulimit, bg and etc aren't utils they are commands from bash 😄

Just type man bash to check others.

Precondition

TBD

Fill multilines data into a file without an editor

$ cat <<EOF> <path_to_file>
one line
second line
third line
EOF

The simple circle

$ for FILE in *; do echo ${FILE} - Foo; done

Find file in filesystem

/ - The path where find object

type f - The type is a file

type d - The type is a directory

name - The name object for find

-print - Additional action, like example is print

$ find / -type f -name "README.*" -print

Move job in the background

$ sleep infinity &

Show jobs in background

$ jobs

Join to background

$ fg 1

Strong recommend to use aliases

Aliases are extended function in bash and that can reduce your operations.

$ alias tailf='tail -f'
$ alias ll='ls -la'

Kill process

In case terminate a process

Common using signals:

 1       HUP (hang up)
 2       INT (interrupt)
 3       QUIT (quit)
 6       ABRT (abort)
 9       KILL (non-catchable, non-ignorable kill)
 14      ALRM (alarm clock)
 15      TERM (software termination signal)

$ kill -<signal_id> <pid>

Pipe or conveyer

• Pass value as arguments to the pipeline

# ls /home/*/.ssh/authorized_keys | xargs -I {} bash -c "echo -n {}; cat {}"

• Check counts to target IP

ss -tan | grep EST | grep <IP_DEST> | awk '{ print $4 }' | tr ":" " " | awk '{ print $1 }' | sort | uniq -c

bashrc

• Connect to host with specific port and separate ":" by ssh

Update bashrc or zshrc file

# ssh 127.0.0.1:2888

function ssh() {
  if [[ "${1}" == *":"* ]]; then
    ARG_HOST=$(echo "${1}" | cut -d : -f 1)
    ARG_PORT=$(echo "${1}" | cut -d : -f 2)
    /usr/bin/ssh ${ARG_HOST} -p ${ARG_PORT} ${@:2}
  else
    /usr/bin/ssh $@
  fi
}