Shell Programming and Scripting

hey all,

./test

Code:

#!/bin/bash
for line in $(cat data1)
do
echo $line
done

data1

Code:

ello there
nobody says a word

Output after running the file :

Code:

hello
there
nobody
says
a
word

While output should be this :

Code:

hello there
nobody says a word

Could anyone explain/fix this?

I could use other kinds of loops that would do the job! but I am interested in understanding this kind of loop.

thanks a lot.

The input to for is a list of tokens separated by the characters defined in the internal field seperator (IFS) variable; usually space, tab and newline. For example:

Code:

for x in one two three 
do
   echo "$x"
done

Will set the variable x to each of the three tokens on the line and then echo those tokens out, one per line:

Code:

one
two
three

In your example, you use cat to supply the tokens which are space separated words. The shell then runs one iteration of the loop for each of the tokens and as you discovered you end up with one word printed per line.

As you said, there are better ways to do this. For the sake of anybody who comes across this thread unsure of how:

Code:

while read rec
do
   echo "$rec"
done <file

Code:

for line in $(cat data1)...

using for x in... is using values delimited by space, not newline, if you want to use your code as it is you must change the delimiter to newline:
EDIT: IFS seems to be space, tab or newline by default.

Code:

#! /bin/bash
OLDIFS="$IFS"
IFS=$'\n'
for line in $(cat data1); do
  echo $line
done
IFS="$OLDIFS"

(thanks to this post: I'm sure there are better ways to achieve the result you want, but you wrote that you want to understand why it's not working as you expected.

Better way you should use this...

Code:

for line in "$(cat data1)"
do
echo "$line"
done

ello there
nobody says a word

Regards
pamu

No, that is a useless use of cat and dangerous use of backticks, and doesn't work properly. It will split on any spaces, not just newlines.