Reading multiple lines user input in Shell

Question

Hi I have a program where if the user inputs a filename I read form the file else I will prompt them for input.

Currently I am doing:

    input=$(cat)
    echo $input>stdinput.txt
    file=stdinput.txt

The problem with this is it doesn't read the newline characters in input, for example if I input

s,5,8
kyle,5,34,2 
j,2

output

s,5,8 k,5,34,2 j,2

The intended output to be stored in a file is

s,5,8
kyle,5,34,2 
j,2

I need to know how to include the newline character while reading.?

hek2mgl · Accepted Answer · 2013-11-01 22:49:19Z

4

echo will suppress the newlines. You don't need the additional $input variable as you can directly redirect cat's output to the file:

file=stdinput.txt
cat > "$file"

Also it makes more sense for me to define $file before the cat. Have changed this.

If you need the user input in both the file and $input then tee would suffice. If you pipe the output of cat (user input) to tee the input will be written to both the file and $input:

file=stdinput.txt
input=$(cat | tee "$file")

edited Nov 1, 2013 at 22:49

answered Nov 1, 2013 at 22:32

hek2mgl

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2 Comments

sa_nyc Over a year ago

I tried but when I cat the file i.e. cat $file it doesn't show anything.

hek2mgl Over a year ago

cat $file works for me (means content is in the file).. But with my previous solution $input was empty. Have changed this and use tee now

damienfrancois · Accepted Answer · 2013-11-01 22:40:49Z

2

Try quoting the variable while echoing it:

input=$(cat)
echo "$input">stdinput.txt
file=stdinput.txt

Example:

$ input=$(cat)
s,5,8
kyle,5,34,2 
j,2
$ echo "$input">stdinput.txt
$ cat stdinput.txt 
s,5,8
kyle,5,34,2 
j,2
$

while indeed, not quoting the variable leads to the situation you describe

$ echo $input>stdinput.txt
$ cat stdinput.txt 
s,5,8 kyle,5,34,2 j,2
$

answered Nov 1, 2013 at 22:40

damienfrancois

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Comments

Dmitriusan · Accepted Answer · 2013-11-01 22:40:37Z

0

You may use such syntax:

#!/bin/sh

cat > new_file << EOF
This will be line one
This will be line two
This will be line three
   This will be line four indented
Notice the absence of spaces on the next line
EOF

Here cat reads text until it encounters delimeter (EOF in our case). Delimeter string may be anything.

answered Nov 1, 2013 at 22:40

Dmitriusan

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Comments

Cole Tierney · Accepted Answer · 2013-11-01 22:45:39Z

0

Would printf help?

printf "$input">stdinput.txt

answered Nov 1, 2013 at 22:45

Cole Tierney

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