how to modify a text file or a string in shell programming

luckyvietman · 05-28-2005, 04:50 AM

Please show me what command to modify a text file or a string .
Example :
I have a text file "a.txt" , its character in line 5 and column 10 is 'x' and I want to replace it with 'y' character. How can i do this ?

and in string . I have a variable $somestring="This is some string" . The first character of this string is ' T ' and i want to replace it with character ' t ' . How can i do it ?

help me, please. Thank you very much !

druuna · 05-28-2005, 04:59 AM

Hi,

Looks like homework, although I'm not sure

So here are some pointers you could look into:

grep -> Look for a string in a file/variable
sed -> replace a string with something else.

Examples:

grep "dummy" some.file => greps any line containing dummy in some.file
sed 's/THEN/THAN/g' => Chnage THEN into THAN (case sensitive), on the whole line (the g).

Take a look at the manpages for all the options.

Hope this helps.

trutnev · 05-28-2005, 08:08 AM

gawk -v var=y -F '' 'NR==5 {$5=var; for( i = 1; i <= NF; i++) printf"%s", $i; printf "\n"}; NR!=5' a.txt

this is to replace exactly the 10th character on the 5th line

to be more generic, you should use sed and grep

to lower the characters, use the tr command

Quote:

Originally posted by luckyvietman
Please show me what command to modify a text file or a string .
Example :
I have a text file "a.txt" , its character in line 5 and column 10 is 'x' and I want to replace it with 'y' character. How can i do this ?

and in string . I have a variable $somestring="This is some string" . The first character of this string is ' T ' and i want to replace it with character ' t ' . How can i do it ?

help me, please. Thank you very much !

jpgoper · 07-11-2005, 08:58 PM

I tried with:

Quote:

for file in $(grep "oldtext" /home/onedir/*)
do
sed 's/oldtext/newtext/g' $file >/tmp/$$ && mv /tmp/$$ $file
done

old/unwanted text is:
<script type ="text/javascript" src='http://www.business-plan-development.com/astracker/ast.php'></script>

new text:
<? include($ruta."/include/clicks.php");?>

and it doesn't work, it gives me a prompt ">" as if it was waiting for aditional code. The problem is with sed, because when changed sed for echo, it ends well.

I got the same problem when using:

Quote:

find . -name '*.html' | xargs perl -pi -e 's/oldtext/newtext/g'

can anyone help me? please!

exvor · 07-12-2005, 03:32 PM

wow this would be eazier in c then in bash
lol go figure

mabye you could use a macro for vi or something but im not too familliar with bash scripting.

sorry

vladmihaisima · 07-12-2005, 05:08 PM

Are you replacing literarly oldtext with the line you specified ?

In that case you should escape the " and / . Like :

Code:

A="<script type =\"text\/javascript\" src='http:\/\/www.business-plan-development.com\/astracker\/ast.php'><\/script>"
sed "s/$A/newtext/g"

(of course, same with new text).