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How to replace a whitespace with line break?

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# 1  
Old 03-23-2014
Linux How to replace a whitespace with line break?
Hello, I am a beginner in Unix and I'm learning how to program by myself.

I am trying to create a shell script that is able to take in either a file containing input or by standard input, and replacing every whitespace with a new line break.

so basically the input would be

This <SP> is <SP> a <SP> line. # where <SP> is a space

and the output would return

This
is
a
line.

so far i have understood the concept of using
Code:
while read line

, and as such has came up with the following code so far

Code:
#!/bin/bash

while read line; do
echo "$line"
done

but this only outputs correctly when there is a real line break instead of a whitespace in the file/stdin.

How should I modify the code to break every whitespace as a new line? Regards.
# 2  
Old 03-23-2014
Try:
Code:
tr ' ' '\n' < file

# 3  
Old 03-23-2014
Quote:
Originally Posted by bartus11
Try:
Code:
tr ' ' '\n' < file

That kinda worked. However, when I tried using a test case with a tab or with more than one space included, it stopped working.

Input:

This <SP> is <TAB> <SP> a <SP> <SP> <SP> line.

and it would only give the output:

This
is
a


line.

instead of the desired output:

This
is

a



line.

What is going on? Could I get an explanation?
# 4  
Old 03-23-2014
TAB is a different character from space. To replace spaces and TABs you can try:
Code:
tr ' \t' '\n' < file

# 5  
Old 03-23-2014
Technically, whitespace is more than just the space character. It includes a blank space, form feed, vertical and horizontal tabs and newline.

Code:
tr '[:space:]' '\n' < file

This User Gave Thanks to fpmurphy For This Post:
fozilla
# 6  
Old 03-24-2014
Quote:
Originally Posted by fpmurphy
Technically, whitespace is more than just the space character. It includes a blank space, form feed, vertical and horizontal tabs and newline.

Code:
tr '[:space:]' '\n' < file

If I understand correctly, the < file at the end is feeding the file into the script, right? But right now I'm trying to do it in a way so that its like:

./test.sh FILENAME #file input

and

./test.sh #this reads from standard input

So how do I approach this?
# 7  
Old 03-24-2014
Just do some check for the arguments
Code:
$ cat test.sh
#!/bin/sh
if [ $# -eq 0 ];then
    while read -r line
    do
        case "$line" in
            quit|Quit)
                exit 0;;
            *)
                echo "$line"|tr '[[:space:]]' '\n';;
        esac
    done
else
    for i in $@
    do
        if [ "$i" = '-' ];then
            trap '"break"' INT
            while read -r line
            do
                echo "$line"|tr '[[:space:]]' '\n'
            done
        else
            while read -r line
            do
                echo "$line"|tr '[[:space:]]' '\n'
            done<"$i"
        fi
    done
fi

cheer up.
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