How to find and replace the text in shell script

Question

I am a new bie to shell scripting, here i am trying to find the text and replace the text using the shell script.

what i am trying to do is, actually i have a text file which has 2 strings separated by ": "

Like this

lorem:ipsum
dola:meru
etc....

my script will take 2 parameters while running. now the script should check if first parameter is found or not if not found it should add it to text file.

if the first parameter is found, then it should replace the second parameter.

for example

The text file has data like this

lorem:ipsum
dola:meru
caby:cemu

i am running my script with 2 parameters like this

./script.sh lorem meru

So when i run the script it should check if the first parameter found in the file if found, the script should replace the second string..

i.e I ran the script like this

./script.sh lorem meru

so in the file

lorem:ipsum
dola:meru
caby:cemu

after running the script, in the line

lorem:ipsum

should get replaced to

lorem:meru

here is what i have tried..

#!/bin/sh
#
FILE_PATH=/home/script
FILE_NAME=$FILE_PATH/new.txt

echo $1
echo $2 
if []   then     
else 
echo $1:$2 >> $FILE_NAME
fi

devnull · Accepted Answer · 2013-10-01 12:49:06Z

2

Using sed might be simpler.

$ cat inputfile 
lorem:ipsum
dola:meru
caby:cemu
$ pattern="lorem"
$ word="meru"
$ sed "/^$pattern:/ s/:.*/:$word/" inputfile 
lorem:meru
dola:meru
caby:cemu

answered Oct 1, 2013 at 12:49

devnull

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Comments

Kent · Accepted Answer · 2013-10-01 12:51:36Z

1

try this line in your script:

 awk -F: -v OFS=":" -v s="$1" -v r="$2" '$1==s{$2=r}7' file > newFile

answered Oct 1, 2013 at 12:51

Kent

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Comments

Abu · Accepted Answer · 2015-03-12 07:21:08Z

You can try this as well,

input file : new.txt

lorem:ipsum
dola:meru
caby:cemu

Script file: script.sh

#!/bin/sh
sed -i "s/$1:.*/$1:$2/" new.txt

if you run the script as u wished "./script.sh lorum meru"

Output: new.txt, will be displayed as

lorem:meru
dola:meru
caby:cemu

Explanation: sed is a powerful text processing tool, where u can manipulate the text as you wish with the options it provides.

Brief explanation of the code, sed -i > used to replace the contents of the original file with the new changes ( if u dont give -i in sed it will just print the modified contents without affecting the original file)

"s/old:.*/old:new/"

"s" is used for substitution. Syntax is "s/old/new/'. Here * specifies anything that is present after the ":" So by executing this you will get the desired output.

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