Perl. Replace text in file.

Substitute text in a file in-situ

perl -i -pe 's/1234/4321/g' filename

-i edits file in-situ.
-p loops through each filename and prints out each line.

Convert Upper case to lower case

perl -i -pe 'tr/A-Z/a-z/' x

Shell scripting: case statement & numbers

Selecting a numeric range with the case statement.

case ${NUMBER} in
        [0-9]|[0-6][0-9]|7[0-5])
                                echo "${NUMBER} <= 75"
       ;;
       [7-8][0-9]|9[0-5])
                               echo "75 < ${NUMBER}<=95"
       ;;
       [9][5-9]|100)
                                echo "95< ${NUMBER} <=100"
       ;;
esac

Shell scripting: Testing empty variables

$V="xNotEmpty"

if [ x$V = "xNotEmpty" ]
then
       echo "\$V not empty"
else
       echo"\$V is empty"
fi

Or:

if [ "$V" = "" ]
then
      echo "\$V is empty
fi

awk

Using shell variables with awk.

1. awk "/$func/"'{print $0}' filename

2. awk -v pat=$func '/pat/{print $0}' filename

Using fields in search pattern

For a similar match:

1. awk '$1~/pattern/{print $0}' filename

For a precise match:

2.  awk -F":" -v user=$U '$1 == user {print $0}' filename

Perl command line.

Using multiple perl commands on the command line.

perl -n -e 'perl cmd;'\
-e 'perlcmd'

Invoke the split command

perl -n -a -e 'cmd'

-n Places a loop around the command line.

My .vimrc file

syntax on
set viminfo^=h
set ruler
set nohls
set incsearch
set showmatch
set ts=4 sw=4
syntax enable
set hlsearch
"Use F4 to switch high lighting on/off
:noremap <F4> :set hlsearch! hlsearch<CR>

Shell Scripting: Special Variables

$?        Exit status or return code of last command.
$#        Number of arguments.
$@        Argument 1 thru n with Input Field Separator.
$*        "$1" $2" ... $n.
$!        Process id of last background process.
$$        Process id of shell running this script.
$-        The current shell flags.

Searching for SUID & SGID files.

find / \( -user root -perm -004000 -o -perm -002000 \) -type f -print