Linux Shell Programming. Implementing a Search, Find and Replace Technique

Question

I have to implement an application in shell programming (Unix/Linux).

I have to search a word from a text file and replace that word with my given word. I have a knowledge on shell and still learning.

I am not expecting source code. Can anybody help me or suggest me or give me some similar solution....

You can for example use `grep` to find text in a file, `find` to find a file and `sed` for replacements. Check man page of each one of them (`man grep`, `man sed`...). — fedorqui, Mar 26 '14 at 14:22
`embedded-linux` seems an odd tag for this question, as does `linux-kernel` — William Pursell, Mar 26 '14 at 14:34

score 0 · Answer 1 · edited May 10 '16 at 09:19

0

cat abc.txt | grep "pattern" | sed 's/"pattern"/"new pattern"/g'

The above command should work

Thanks,

Regards,

Dheeraj Rampally

edited May 10 '16 at 09:19

fluter

answered Mar 26 '14 at 21:32

Dheeraj R

2

I smell a "useless use of cat" award...http://en.wikipedia.org/wiki/Cat_%28Unix%29#Useless_use_of_cat ;-) – Gary_W Mar 27 '14 at 15:26

score 0 · Answer 2 · edited May 23 '17 at 12:09

Say you are looking for pattern in a file (input.txt) and want to replace it with "new pattern" in another (output.txt)

Here is the main idea, without UUOC:

<input.txt sed 's/"pattern"/"new pattern"/g' >output.txt

todo

Now you need to embed this line in your program. You may want to make it interactive, or a command that you could use with 3 parameters.

I tried to avoid the use of output.txt as a temporary file with this:

<input.txt sed 's/"pattern"/"new pattern"/g' >input.txt

but it empties input.txt for a reason I can't understand. So I tried with a subshell, so:

echo $(<input.txt sed 's/pattern/"new pattern"/g')>input.txt

... but the echo command removes line breaks... still looking.

From https://unix.stackexchange.com/questions/11067/is-there-a-way-to-modify-a-file-in-place , it looks like writing to the very same file at once it not easy at all. However, I could do what I wanted with sed -i for linux only:

sed -i 's/pattern/"new pattern"/g' input.txt

From sed -i + what the same option in SOLARIS , it looks like there's no alternative, and you must use a temporary file:

sed 's/pattern/"new pattern"/g' input.txt > input.tmp && mv input.tmp input.txt