Say if i wanted to do this command:
(cat file | wc -l)/2
and store it in a variable such as middle, how would i do it?
I know its simply not the case of
$middle=$(cat file | wc -l)/2
so how would i do it?
views:
176answers:
5I'd prefer not to use awk to be honest, there is a way to do it without it, im just reading a book and it says not to use sed or awk
KP65
2010-02-22 21:40:41
the above command can be done without `wc`. just `awk` will do.
ghostdog74
2010-02-23 00:30:06
We have a winner. And just as I got back from reading the man page, too. (I generally script to vanilla /bin/sh, so I always have to look up bashisms)
dmckee
2010-02-22 21:43:21
@blahdiblah: Did you notice how the OP used `$()` instead of backticks? Also, it's good that you corrected the useless use of `cat`, but then you replaced it with a useless use of redirection. `wc` accepts filenames as arguments. Also, `wc` outputs the filename which needs to be stripped off before you can do the division.
Dennis Williamson
2010-02-23 01:09:08
@dennis, the redirection has a "purpose". It eliminates the file name, giving just the number of line count.
ghostdog74
2010-02-23 01:30:56
A:
When assigning variables, you don't use the $
Here is what I came up with:
mid=$(cat file | wc -l)
middle=$((mid/2))
echo $middle
The double parenthesis are important on the second line. I'm not sure why, but I guess it tells Bash that it's not a file?
jonescb
2010-02-22 21:44:21
A:
using awk.
middle=$(awk 'END{print NR/2}' file)
you can also make your own "wc" using just the shell.
linec(){
i=0
while read -r line
do
((i++))
done < "$1"
echo $i
}
middle=$(linec "file")
echo "$middle"
ghostdog74
2010-02-23 00:28:28
A:
This relies on Bash being able to reference the first element of an array using scalar syntax and that is does word splitting on white space by default.
middle=($(wc -l file)) # create an array which looks like: middle='([0]="57" [1]="file")'
middle=$((middle / 2)) # do the math on ${middle[0]}
The second line can also be:
((middle /= 2))
Dennis Williamson
2010-02-23 01:16:19