modifying a file in shell (via sed ?)

Shautieh · 09-15-2006, 01:34 PM

Hello

here is my problem : i want to change one line of a file with another, but can't find how to do it :[
from what i've seen on the net, i should use sed, but i have a big problem with it because of some slashes that mess up the command line....

>

Quote:

#!/bin/bash
images=$(find /home/babou/classes/ -type f $ -name "*.svg" -o -name "*.png" $ -printf "%p;")
# now i have in image all the pngs and svgs in the directory

sed -e 's/beginning=.*/'$images'/' ~/bibi/file
# that should change the line in "file" with "beginning=" in it with $images

i'm not used to shell so it took me some time to see where is the problem, and in fact it is because there are "/" in $images so that sed has too much "arguments" (as it uses "/" to separate the "arguments")

so, do you see a way to put a "\" ahead of each "/" in $image ? (i can't use sed either, obviously), or is there a simpler way (i'm sure there is one >

)

any help is welcomed :=)

druuna · 09-15-2006, 01:37 PM

Hi,

You don't need to use / as a seperator for sed. It can be anything you want.

So instead of s/../../, try s%..%..%

Hope this helps.

Shautieh · 09-15-2006, 01:47 PM

you are a god !

i've spent some hours with this problem, finding nothing on the net and with your answers it works great now

i saw nowhere that we could put other things than slashes

....
are there other possibilities instead of "/" and "%" ?? (if one day i have a problem with "%" too

druuna · 09-15-2006, 01:57 PM

Hi,

To my knowledge it can be any 'normal' character.

There's also the 'classical' approach: Escape all the special characters.

Code:

$ THISVAR="/foo/bar"
$ echo $THISVAR
/foo/bar
$ echo $THISVAR | sed 's/\//@/g' # using / as seperator. 'classic'
@foo@bar
$ echo $THISVAR | sed 's%/%@%g' # using % as seperator
@foo@bar
$ echo $THISVAR | sed 'sA/A@Ag' # using A as seperator
@foo@bar

Hope this clears things up.

Shautieh · 09-15-2006, 02:23 PM

it is really clear now thanks to you

i didn't thought sed command would be this supple

/bin/bash · 09-17-2006, 04:34 AM

The pipe '|' is a good substitute for '/'. Makes sed more readable IMO.

sed -e 's|/some/file/path|/new/file/path|g'
As opposed to this:
sed -e 's/\/some\/file\/path/\/new\/file\/path/g'

soggycornflake · 09-18-2006, 02:17 PM

Indeed you can use any character instead of /. From the sed info manual:

Quote:

The syntax of the `s' (as in substitute) command is
`s/REGEXP/REPLACEMENT/FLAGS'. The `/' characters may be uniformly
replaced by any other single character within any given `s' command.
The `/' character (or whatever other character is used in its stead)
can appear in the REGEXP or REPLACEMENT only if it is preceded by a `\'
character.

Note that you can use _any_ character, even control characters (except nul), though I can't think why you'd want to.

P.S. I often use a comma as the small size is unobtrusive (and easy to type).

Shautieh · 09-19-2006, 05:14 AM

thanks, a coma or more especially a pipe are good ideas as it is generally not seen in what comes afterwards

i think i'll use the pipe more, because there is very little chance to find it in what comes afterwards, while there may be a coma if it is a phrase

but anyway it is very nice to see all these opportunities, and i don't understand why they preconize slashes by default, i lost some hours on this the other day lol

but yeah, thanks, it's all good now