Linux:bash:about "delete key"

When I use "delete key" in some bash terminal, the key sends a tilde "~" instead of deleting the char that is supposed to be deleted.

Find a solution:
1. In your $HOME directory, create or edit your keyboard-mapping file, $HOME/.inputrc
2. Add one mapping line:

"\M-[3~": delete-char

3. restart your terminal

Linux:Shell:Bash: how to search slash or backslash by sed

It is tricky to search (or replace) signs slash '\' or backslash '/' by sed. By searching internet, I found 2 approaches:

1. Put the command line of sed to a file called my.sed:

/D\\O/p

(this will print a line containing 'D\O')

2. Another way is to use single quote instead of double one in your shell command line:

sed -n '/D\\O/ p' myfile.txt

(-n is prevent from printing)

Linux:shell:BASH: How to delete one line by sed

If you want to delete one line containing one word "ThisWord" by sed, then you can do in the way:

sed -i "/ThisWord/d" YourTextFile.txt

Note, here '-i' is to delete it from the original file. Without it, sed only prints the file on screen. So before using '-i', make sure you are doing correct things.

Linux:shell:Bash: How to change color of your shell printout

You could use 'echo -e' to change your printout text and background color by some color variables. One of the easiest ways to use them is to define shell variable, for example, define those variables in your shell script:

red='\e[0;31m'
RED='\e[1;31m'
blue='\e[0;34m'
BLUE='\e[1;34m'
cyan='\e[0;36m'
CYAN='\e[1;36m'
NC='\e[0m' # No Color

. '\e[0;36m': 0's place is the color of background (0, no effect, 1, bold, 4, underline) and 36 is the text color. You also can change background colors due to color values in the color table. For example, '\e[41;34m' changes background color to red and text color to blue.

How to print?

echo -e "$red These texts are in red$NC" #you must use '-e' to enable interpretation of the backslash-escaped characters, see echo's help.

or if you want to use it in 'printf':

printf "%s\n" "`echo -e $red`These texts are in red`echo -e $NC`"

There is a table of color values attached (this table is from the link). You can find color values what you want.

linux:shell:bash:grep: multi-grep

If I want to search multi words by grep, I could do in the way:

egrep "a|b|c|d" my_input_file.txt

then egrep will help you to search OR of a, b, c and d. If searching for AND of multi-words, you can do by pipe:

grep a my_input_file.txt |grep b |grep c |grep d

. However, sometimes, it is not so easy to use pipe in one line for the above usage. You can always build string of the command first and evaluate it. For example,

cmd="grep $var1 my_input_file.txt|grep $var2"
...
cmd="$cmd |grep $var3"
...
eval $cmd

Shell:Bash:replace substring in string

${string/substring/replacement} Replace first match of $substring with $replacement
${string//substring/replacement} Replace all matches of $substring with $replacement
${string/#substring/replacement} If $substring matches front end of $string, substitute $replacement for $substring
${string/%substring/replacement} If $substring matches back end of $string, substitute $replacement for $substring

Refer to the link for more information.

Linux:Bash:how to print quotation marks in awk

ls | awk '{print "'\''"$1"'\''"}'

or

awk 'BEGIN { print "Here is a single quote \47" }'

Linux:shell:grep how to use grep's result

mystr="IloveChina"
echo $mystr |grep China
echo $? #this will return 0
echo $mystr |grep USA
echo $? #this will return 1
#so you could use this returned value to justify if grep found the string.
# Or you use how many searched results returned to do this, for example,
echo $mystr |grep -c China # return 1 to you
echo $mystr |grep -c USA # return 0 to you
# so simply, you can use the number to justify if you found the results like
if [ `echo $mystr |grep -c China` -ge 1 ]; then
echo "Yes, you are"
fi

Linux: alias: shell: define your alias in Linux

Except /etc/profile, ~/.bashrc and ~/.bash_profile, you can add alias into the file:

/etc/profile.d/alias.sh (or alias.csh for c shell)

This file is effective for all users like /etc/profile.

SHELL: add head to a bash script

Every time when you write shell script, it is sick to type the same head on every script? If you are, try this small script to add head to your code.

#!/bin/sh
help(){
echo "Usage: "
echo " `basename $0` "
echo " `basename $0` -h "
exit 1
}

if [ $# -lt 1 ] || [[ $1 = -h ]]
then
help
fi

echo " "
echo "Input the title of your code:"
read line
newline[0]='#!/bin/sh'
newline[1]="#######################################"
newline[2]="# $1"
newline[3]="# $line"
newline[4]="# "
newline[5]="# Created by Your name (you@email.com)"
newline[6]="# on `date`"
newline[7]='# Usage: '
newline[8]='# '
newline[9]='# Modifications: '
newline[10]='# '
newline[11]='#######################################'
newline[12]=' '
newline[13]='help() {'
newline[14]=' echo ""'
newline[15]=' echo "Usage: $0 <>"'
newline[16]=' echo " <>"'
newline[17]=' echo " -h or no-args for this help info."'
newline[18]=' echo ""'
newline[19]='}'
newline[20]='if [[ $1 == "-h" ]] || [ $# -lt 1 ]'
newline[21]=' then'
newline[22]=' help'
newline[23]=' exit 0'
newline[24]='fi'

#this total value must be equal to the last index!!!
total=24
index=0
while [ $index -le $total ]
do
((iline=index+1))
sed -i "${iline}i\\${newline[$index]}" $1
((index+=1))
done




SHELL: a very good e-reference about bash

An excellent reference about bash is here. It descripts bash in a very detail. I have some small bash scripts. Later I will post them here for sharing.