How to extract data and for loop it into an array? (shell)

WeiSomething · 11-16-2006, 07:50 PM

Hi everyone!

How do I do a split in UNIX? Like what a Java can do where it read in a file and split the data with the delimiter the user specified and put all the data it split into an array.

And how do I read a specific line in a file?

For example:

Data1

I love apple
I love orange
I love mango

How do i extract the second line "I love orange" out?

unSpawn · 11-16-2006, 09:10 PM

How do I do a split in UNIX? Like what a Java can do where it read in a file and split the data with the delimiter the user specified and put all the data it split into an array.
#Watch your IFS (delimiters)

Code:

ARRAY=(`output something`); 
echo ARRAY has ${#ARRAY[@]} elements.

And how do I read a specific line in a file?

Code:

cat file | while read line; do case "${line}" in *orange) doSomething;; esac; done

or

Code:

n=1; cat file | while read line; do [ $n -eq 2 ] && doSomething; ((n++)); done

Code:

function help() { echo "Bash scripting guides:
http://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html 
http://www.tldp.org/LDP/Bash-Beginners-Guide/html/index.html 
http://www.tldp.org/LDP/abs/html/"; }

WeiSomething · 11-16-2006, 11:56 PM

Quote:

Originally Posted by unSpawn

How do I do a split in UNIX? Like what a Java can do where it read in a file and split the data with the delimiter the user specified and put all the data it split into an array.
#Watch your IFS (delimiters)

Code:

ARRAY=(`output something`); 
echo ARRAY has ${#ARRAY[@]} elements.

How do I set my IFS (delimiters) to an empty space?

file1
I love apple
I love orange
I love mango

Code:

ARRAY=(`more file1`); 
echo ARRAY has ${#ARRAY[@]} elements.

Does this print out "ARRAY has 9 elements."?

What I got is 1 element.

Tinkster · 11-17-2006, 12:39 AM

IFS='<something>'
It's a space by default, hence 9 elements. If you want one line = one element,
use IFS="\n"... if you see 1 element there's something seriously odd with your
system ...

Cheers,
Tink

WeiSomething · 11-17-2006, 01:41 AM

Quote:

Originally Posted by Tinkster

IFS='<something>'
It's a space by default, hence 9 elements. If you want one line = one element,
use IFS="\n"... if you see 1 element there's something seriously odd with your
system ...

Cheers,
Tink

hi. I know why I got only 1 element. Because I did not put any bracket around it. But after I put, it gave mi error like:

New1.sh[4]: syntax error at line 4 : `(' unexpected

ARRAY=(`more file1`); <-- this is the line that it prompt me with the error.

WeiSomething · 11-17-2006, 02:45 AM

Quote:

Originally Posted by WeiSomething

hi. I know why I got only 1 element. Because I did not put any bracket around it. But after I put, it gave mi error like:

New1.sh[4]: syntax error at line 4 : `(' unexpected

ARRAY=(`more file1`); <-- this is the line that it prompt me with the error.

I found out that the method is not correct in fact it should be:

Code:

set -A array1 `more test_file`

But now i had problem with the LFS because in my file there is space and new line. How to define 2 delimiters?

bigearsbilly · 11-17-2006, 03:27 AM

you can't have 2 delimiters. (not in ksh, which it looks like)

If you want to ignore blank lines
you can set -A array1 `grep . test_file`

you probably shouldn't really use 'more' as it's designed for interactive use
use 'cat' instead.