Bash

manual, refs

• Mendel Cooper - Advanced Bash-Scripting Guide (aka. ABS) (한글판)
• Bash Reference Manual
• bash features
• BASH Programming - Introduction HOW-TO ★
• Bash Guide for Beginners
• Bash scripting Tutorial

$SHLVL

The variable tracks your shell nesting level

$ echo $SHLVL
1
$ bash
$ echo $SHLVL
2
$ exit
$ echo $SHLVL
1

http://stackoverflow.com/a/4511483/766330

Regular expression match test

Use double bracket and =~

if [[ $gg =~ ^....grid.*$ ]] ; then echo $gg; fi

[1]

getopt

long options

use getopt(not getopts) [2]

multiple arguments with one flag

깔끔한 방법이 없어보임. [3]

-o a1 -o a2 -o a3

이런식으로 계속 주는 수밖에 없는듯

default option getopt

$ getopt -s bash -o l:: -l list:: -- -ltest
 -l 'test' --
$ getopt -s bash -o l:: -l list:: -- --list foo
 --list  -- 'foo'
$ getopt -s bash -o l:: -l list:: -- --list=foo
 --list 'foo' --

::을 쓰면 되지만, optional argument를 명시할 때는 short option의 경우 option뒤에 바로 붙여야 하고 long option의 경우 =을 꼭 써주어야 한다. [4]

bash expansion : ranges

$ echo {d..h}
d e f g h

$ echo {d..Z}
d c b a _ ^ ]  [ Z

For more information, refer wiki.bash-hackers.org.

redirection

### cp file1 file2와 같다
$ cat < file1 > file2

string : $''

$ # Single quotation in single qoute
$ # http://stackoverflow.com/a/16605140/766330
$ echo \'sdlfkjsldf\' | sed $'s/\'//'
sdlfkjsldf'
$ #   $'string' : this is special.
$ #   below line won't work.
$ #   echo \'sdlfkjsldf\' | sed 's/\'//‘

[5]

or

$ # 'or' 
$ if [ -z "$1" ] || [ -z "$2" ]; then
>    echo "Usage: `basename $0` rslt_file target_folder"
> fi

ref. expressions used with if

extract tar archive from stdin

use - as the input file

cat largefile.tgz.aa largefile.tgz.ab | tar zxf -

[6]

find out what is using TCP port 80

# netstat -tulpn | grep :80

-p : You should be root

[7]

read from file or stdin

while read line 
do
  echo "$line"
done < "${1:-/dev/stdin}”

${1:-…} takes $1 if defined otherwise the file name of the standard input of the own process is used

[8]

no op

:

$ if true; then :; else echo; fi

[9]

Default .bashrc

/etc/skel/.bashrc

[10]

Tar the output on the fly

The same -f - option works for tarring as well.

tar -cf - something | tar -C somefolder -xvf -

GNU tar uses stdio by default:

tar -c something | tar -C somefolder -xv

[11]