Print line for line

pk21 · 12-01-2002, 04:24 PM

how can i open a file and print line for line to the screen in bash???
I was thinking of:

#!/bin/bash
for line in /home/test/list
do
echo $line
sleep 2
done

But this prints each word to the screen in stead of each line in the file.

unSpawn · 12-01-2002, 07:12 PM

... and it should, cuz that's what you asked Bash to do...

#!/bin/bash
cat /home/test/list | while read line; do echo $line; sleep 2; done

If you want to know what went wrong with your script try running it as "bash -x <scriptname>" (and add "2> <scriptname>.log" if you want it logged as well).

pk21 · 12-02-2002, 04:05 AM

Thanks!

crabboy · 12-02-2002, 09:47 AM

The IFS by default is set to any whitespace, "newline, tab, space" if you set the field seperator to be newline only, the script works.

#!/bin/bash

IFS='
'

for line in `cat web.xml`; do
echo $line
sleep 1
done

Hko · 12-02-2002, 01:59 PM

"for line in `cat web.xml`; do"

will cause the script to exit with an error if web.xml is big.
unSpawn's solution doesn't have this problem:

"cat web.xml | while read line ; do"

crabboy · 12-02-2002, 02:48 PM

True, I was just explaining why his script was displaying words and not lines.

pablomme · 03-16-2004, 07:25 AM

Quote:

Originally posted by crabboy
The IFS by default is set to any whitespace, "newline, tab, space" if you set the field seperator to be newline only, the script works.

#!/bin/bash

IFS='
'

for line in `cat web.xml`; do
echo $line
sleep 1
done

This is useful anyway, I think, because I found out that piping the cat output to 'while read line do {' causes the following code to be executed in a sub-shell, so that any variable that you set within do { } done is automatically forgotten after that. So I've got some questions:
1) How to make the 'cat $file | while read line do {' stuff work and not execute the code in a subshell?
2) Or otherwise, how can I make changes done in a subshell persist after exit? For example, if I change dir and want to stay there after the script, or if I set a variable and want to keep it.
3) Apart from all of this, how can I get a specific line (whose number is known) from a file?
Thanks!

bigearsbilly · 03-16-2004, 10:12 AM

Don't forget to SAVE $IFS before you change it.

ifs=$IFS

blah blah

IFS=$ifs

Otherwise someone who calls your script may get some
unwelcome surprises!

You can't persist variables upwards to the calling script, sorry!
You can 'dot' a file like you do your ~/.bashrc which runs inline.

regards, billy

bigearsbilly · 03-16-2004, 10:14 AM

Getting a specific line?

There's a million ways,
how about....

the 50th line?

Code:

      sed -n '50p' file

billy

pablomme · 03-16-2004, 12:01 PM

Quote:

Originally posted by bigearsbilly
Getting a specific line?

There's a million ways,
how about....

the 50th line?

Code:

sed -n '50p' file

billy

Thanx indeed! Didn't figure that out from 'man sed'. Any other of those million ways that you'd like to mention?

pablomme · 03-16-2004, 12:09 PM

> You can't persist variables upwards to the calling script, sorry!
Shame!
> You can 'dot' a file like you do your ~/.bashrc which runs inline.
Don't get that... I've tried to write a script ".env" that sets $ENV to "Hello", but doesn't exist afterwards.. I think I did't understand what you meant.
Thanx!

bigearsbilly · 03-17-2004, 04:04 AM

No no, pablo
when i mean'dot' a file i mean like:
call it with a .

literally, type 'dot' space filename:

Code:

.  file

bigearsbilly · 03-17-2004, 04:12 AM

you can create functions which you can
use for setting environment or changing directory:

e.g
create a file called say, funcs with the following function:

Code:

billym.devserver>cat funcs   # here is a file i created
mycd()
{
    cd $1
}
billym.devserver>pwd
/tmp
billym.devserver>. funcs    # this puts the function into the current env.
billym.devserver>mycd $HOME  # so this now works
billym.devserver>pwd
/export/home/billym