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I am trying to search for a text in a file and store it into a variable.

My file looks something like this:

Type: Furniture
Color: Blue
Version: 1

I am trying to search for the Version number and store it into a variable and increment it. This number is unknown to me when I am searching the file. So far I have something like this. 

VERSIONNUMBER=//Somehow I want to get the version # from the file. 
VERSIONNUMBER=`expr $VERSIONNUMBER + 1'

sed -i "s/Version:.*/Version=$VERSIONNUMBER/" filename

Am I on the right track so far or is there a better way of doing this? I'm having trouble searching for the version number. I keep getting syntax errors. Any help is much appreciated.

VERSIONNUMBER=`sed -i "s/Version:/*" filename`
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2 Answers 2

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6

This is a job for awk

 awk '/Version:/{$2++}1' ./infile > ./outfile

Example

$ awk '/Version:/{$2++}1' ./infile
Type: Furniture
Color: Blue
Version: 2

Explanation

/Version:/ Match only lines that contain the text 'Version:'

$2++: Get the 2nd field, of which awk delimits with a space by default, and increment it

{...}1: A shortcut to tell awk to print out the lines after it does any alterations

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5 Comments

More precisely, the 1 is a new pattern, one which is always true, with the default action, which is print $0. (An Awk script is a sequence of pattern / action pairs.) Thus awk 1 /etc/passwd is a slower variant of cat /etc/passwd.
Thanks, very clear explanations! This was exactly what I was looking to do except it's much much more simpler. It doesn't seem like I'm able to store the updated version back into the same file so I'm planning to pipe ./infile > ./outfile like you suggested and then replace the old ./infile with the new ./outfile. Thanks again!
@user459811 yes, awk doesn't support inplace edit like sed -i. But note that sed -i is not portable, it's a GNUism. And as im sure you probably already found out, if you attempt to redirect a file onto itself you end up with hosing the file. You'll need to manually copy it over.
I'd not seen the idiom before, so I needed to work out how it worked, to see if it is portable to all versions of awk or not. I believe it is fully portable.
@JonathanLeffler yes, it should be portable. The other idiom I see quite a bit is {$1=$1} if all you want to do is change one of the separators. I used that one just today here. For some reason awk won't change the separators unless it thinks it made a change to one of the fields.
2

If you want to overwrite the file in situ, then you can use Perl instead of Awk.

perl -i.bak -p -e 's/^(Version: )(\d+)/$x=$2+1,"$1$x"/e' "$@"

The .bak saves a backup of filename in filename.bak; if you don't want the backup, drop the .bak from the command line (but leave the -i there). The e modifier on the regex means treat the replacement as an expression. The values $2 etc are readonly, so save the incremented value to $x and then use that as part of the string. The comma operator evaluates its LHS, then its RHS.

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