Change first char of each line in a file to '0' using /bin/sh

Xa! · 10-25-2004, 03:18 PM

Hello!

I have a file, and I want to write a script, that changes _first_ char of _every_ line of this file to '0'.

Let i have file.txt
--------------
1 1 0 0 1 0 0
0 1 1 0 0 0 0
1 1 1 1 1 1 1
1 1 1 1 1 1 1
--------------
and i want
--------------
0 1 0 0 1 0 0
0 1 1 0 0 0 0
0 1 1 1 1 1 1
0 1 1 1 1 1 1
--------------

I think it could be done with sed -e s/{hm.. what to write here?}/0/ < file.txt, but how?

Hko · 10-25-2004, 03:48 PM

Code:

#!/bin/sh

sed -e 's/^./0/' file.txt

DearWebby · 12-12-2010, 10:00 PM

Quote:

Originally Posted by Hko

Code:

#!/bin/sh

sed -e 's/^./0/' file.txt

Can I use something like that to cut the first n characters from each line?

catkin · 12-12-2010, 10:05 PM

Quote:

Originally Posted by DearWebby

Can I use something like that to cut the first n characters from each line?

That should have been covered in your class sessions or other course resources. LQ is here to help people when they get stuck, not to do people's homework. What have you tried so far?

EDIT:

BTW, if you changed the first character of every line the output would be (in CODE tags so it lines up nicely):

Code:

0-------------
0 1 0 0 1 0 0
0 1 1 0 0 0 0
0 1 1 1 1 1 1
0 1 1 1 1 1 1
0-------------

EDIT2:

Have you learned how to search the online manual database (the man pages) by keywords? Try man -k cut to get a list of commands about cutting. The manual section 1 commands are the most relevant for introductory scripting. You can restrict the list to those with man -k cut | grep '(1)'. When you want to know more about a listed command you can view its man page with, for example, man cut

DearWebby · 12-12-2010, 11:51 PM

I am not privileged enough to be able to attend classes or courses. What I know is from studying helpful answers.