replacing situation with 'sed'

tonypal12 · 10-05-2012, 03:33 PM

I'm trying to do a string replace and want to do the following

A file (test.fil) containing the following amongst other lines

myparam = 777777777

and to replace the pattern "myparam" in the above file and anything after (as the blanks before the = may vary and the numbers after the = sign may vary)

so something like

sed -i s/myparam <and everything after that> /myparam = 1234567/g test.fil

note: the search pattern always begins with myparam

so the result would be

myparam = 1234567

P.S: Remember we cannot do sed -i s/myparam = [0-9]*/myparam = 1234567/g test.fil. The reason being there may or maynot be a blank before or after the '=' character.

custangro · 10-05-2012, 04:20 PM

This should work...

EXAMPLE...

Code:

[root@ /tmp]# cat ,mypa 
myparam = 1234567
myparam= 1234567
myparam      = 1234567
myparam	= 1234567
myparam				= 1234567

[root@ /tmp]# sed -e 's/^myparam/other/g' ,mypa 
other = 1234567
other= 1234567
other      = 1234567
other	= 1234567
other				= 1234567

frob23 · 10-07-2012, 04:15 PM

This sounds an awfully lot like a homework question.

If it's not, I still need clarification: we're not replacing the "key" (myparam in your example) but we are replacing everything after it.

So:

Code:

junk     = 435323245
foo = 34
junk = dsd32324
bar    = 5643224

Running the command with "junk 23skidoo" would change the file to:

Code:

junk = 23skiddo
foo = 34
junk = 23skiddo
bar    = 5643224

Am I right?

frob23 · 10-07-2012, 04:57 PM

I am going to go against my gut feeling and assume this isn't homework. Besides, it's a pretty simple thing.

I did this by putting the sed command in a simple script (called switch.sh on my system). You could do it as a command by replacing the variables with the values you want in the sed command from the script. But I assume you'll run this command more than once so having a simplified interface is beneficial.

switch.sh

Code:

#!/bin/sh
PARAM="$1"
VALUE="$2"

sed "s/${PARAM}[        ]*=.*/${PARAM} = ${VALUE}/"

Note: The white-space between the []s is a single space and a tab.

We would use this like follows:

Code:

cat test.fil | switch.sh foo 149234

It outputs the new file to standard out where it can be captured. This handles the following file correctly:

Code:

foo   = bar
foo=454355645
food=454355645
foo df=454355645
bash = 12343
foo =    dssadfdsa
bash      	= nice
foo		=	not

becomes

Code:

foo = 149234
foo = 149234
food=454355645
foo df=454355645
bash = 12343
foo = 149234
bash      	= nice
foo = 149234

This correctly ignores the key "food" and "foo df". You can change the value of "foo df" by putting the argument to the script in quotes (switch "foo df" 67) but let's hope that isn't a problem you really have to face.