I have a text file that on one of the lines contains "#define VERSION_NUMBER 0011" I need to find that line and assign the 4 digit value "0011" to a variable.
Add a comment
|
2 Answers
VAR=$(cat file | grep "#define VERSION_NUMBER" | awk '{print $3}')
This does seem kind of backwards though. Is it possible to change your build scripts to pass -DVERSION_NUMBER=0011 and define the version number that way? Then it can be stored in a simple language independent text file containing nothing else.
1 Comment
shellter
or
... | awk -F= '{print $NF}', Good luck to all.I would use grep and regex, once grep returns a value, you can assign that value to a bash variable fairly easily. Following is working test code:
$ echo "#define VERSION_NUMBER 0011" > test.c
$ c=`cat test.c | sed -n -e 's/^#define VERSION_NUMBER \([0-9]\{4\}\)$/\1/p'`
$ echo $c
0011
Broken Down
This is the important line:
c=`cat test.c | sed -n -e 's/^#define VERSION_NUMBER \([0-9]\{4\}\)$/\1/p'`
Broken down it is composed of c, the variable name is assigned to the evaluation (`...`) of the sed command. The sed command is where the regex is. What I came up with is:
^: the line starts with#define VERSION_NUMBER: a text literal, this will be character-for-character in the string.\(...\): an escaped set of parens that make up a match portion.[0-9]: in the match, a number exists (0 to 9).\{4\}: the preceding number repeats 4 times exactly.- you could use
*here for any number of matches,\{4,\}for 4 or more, or\{4,6\}for 4-6 matches.
- you could use
$: end of the line
When this is run, sed emits the number, and since we assigned sed's evaluation to c, c now contains that number.
Issues
Possible issues are that this does not take whitespace into account, if there is a tab or space at the beginning or end of this line, it will fail.
Confession: I had to learn a little unix regex to answer this, reference: smugbook.
