Replace fixed strings only

Shell Programming and Scripting
1

Hi All,

I just need to do find and replace in a file....
say for eg I have the input file like below:
in.txt
#####
oldtextoldtext
oldtext
oldtext
oldtext
oldtext123
oldtext-
oldtext

I need to replace oldtext to newtext... my output file should come like below..
out.txt
######
oldtextoldtext
newtext
newtext
newtext
oldtext123
oldtext-
newtext

Pls help me....
Thanks in advance
Saravana

2

what have you tried? put in some effort.

3

Did you try anything?

4

I tried with this cmd :
sed -e 's/oldtext/newtext/g' $file

but it is repalcing all the lines... :frowning:

5

sed 's/^oldtext$/newtext/g' $file

6

Sorry... I forgot add this line in my input file.... If I have the below line in my file then it will not work....

something something oldtext

So it will not work.....

7

there's no need for 'g' as the pattern will appear only ONCE.

8 
sed -e 's/^oldtext$/newtext/' -e 's/ oldtext / newtext /g' -e 's/ oldtext$/ newtext/'  -e 's/^oldtext /newtext /'  input_file.txt
9

(right about the unneeded g)

sed 's/\<oldtext\>/newtext/g'
(not all sed's support this)

almost does what you want except for the "oldtext-" line, since '-' is a word boundary too

10

This substitues all occurances of oldtext that are surrounded either by blanks or by start/end of the line.

sed 's/\(^\|[[:blank:]]\)oldtext\([[:blank:]]\|$\)/\1newtext\2/' filename