Creating files with some content with shell script

Question

I need to configure a server with a few files and I want to do it programmatically.

I need to create files say /home/a.config, /var/spool/b.config, /etc/c.config

Files above have some contents (multi lines).

I want to create ONE shell script which can create all three file with multiple lines (around 10). I would like to know the how can I use CAT command to do that. (inside shell script).

I am looking something like this

echo " going to create  /home/a.config"

cat "HOW CAN I HAVE MULTIPLE LINES HERE?? " >  /home/a.config

thanks

Dennis Williamson · Accepted Answer · 2022-06-28 19:26:14Z

148

You can use a here document:

cat <<EOF >filename
first line
second line
third line
EOF

You can place several of these in the same script.

edited Jun 28, 2022 at 19:26

answered Feb 2, 2011 at 19:52

Dennis Williamson

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6 Comments

Nagev Over a year ago

Note that $ has to be escaped if it's to be included in the actual text.

Dennis Williamson Over a year ago

@Nagev: If you don't want any parameter expansion, command substitution, and arithmetic expansion in the here document you can quote the beginning delimiter 'EOF' instead of having to escape each individual dollar sign.

Júlio Falbo Over a year ago

And if I want to use a parameter value in my text?

Braian Coronel Over a year ago

How do I access an external variable?

Dennis Williamson Over a year ago

@JúlioFalbo: If you don't quote the here doc delimiter (e.g. EOF) then parameters (variables) in the text will be expanded.

|

Allwin · Accepted Answer · 2021-04-26 05:26:20Z

35

file="/tmp/test.txt"
echo "Adding first line" > $file
echo "Adding first line replaced" > $file
echo "Appending second line " >> $file
echo "Appending third line" >> $file
cat $file

> to add/replace the content ( here actual content got replaced by the 2nd line)
>> to append

Result
Adding first line replaced
Appending second line
Appending third line

edited Apr 26, 2021 at 5:26

answered Jul 29, 2016 at 8:22

Allwin

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2 Comments

sarmahdi Over a year ago

I wonder why no one gave you an up vote. Your answer is pretty good too. Thanks works for me.

MonneratRJ Over a year ago

I thought that your answer is pretty much spot on...

Victor Sorokin · Accepted Answer · 2011-02-02 19:46:40Z

11

Like so:

#!/bin/bash

var="your text"
echo "simply put,
just so: $var" > a.config

For further info, see Input/Output part of abs.
Hope, this helps.

answered Feb 2, 2011 at 19:46

Victor Sorokin

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Comments

Deepak Rao · Accepted Answer · 2017-09-20 09:47:56Z

7

If you've got variables like $1 or $HOMEDIR in your text then these normally get evaluated and substituted with actual values. If you want to prevent these from getting substituted then you need to quote the opening limit string (EOF in example below) with single quote 'EOF', double quote "EOF" or precede it with backslash \EOF

Closing limit string stays as is. EOF

This is especially useful if you are writing shell scripts to a file.

cat << 'EOF' >/etc/rc.d/init.d/startup
case $1 in
    start)
        start 
        ;;
    stop)
        stop
        ;;
    restart)
        stop
        start
        ;;
    status)
       pid=$(tomcat_pid)
        if [ -n "$pid" ]
        then
           echo "Tomcat is running with pid: $pid"
        else
           echo "Tomcat is not running"
        fi
        ;;
esac

EOF

Refer Example 19.7 Parameter Substitution Turned off in Here Documents

answered Sep 20, 2017 at 9:47

Deepak Rao

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1 Comment

zookastos Over a year ago

Perfect ! this is exactly what I was looking for

scotjam1981 · Accepted Answer · 2012-12-20 13:46:43Z

1

>\#!/bin/bash
>
>var="your text" <br>
>echo "simply put, <br>
>just so: $var" > a.config

Note that you also need to escape out certain characters to avoid them interfering with what you're trying to do, for example $ ` and " will all break such a statement unless preceded with a backslash, i.e. \` \$ or \"

so if we define the following:

var="100"

the following would not behave as expected:

echo "simply put,
just "lend" me US$ $var" > a.config

but the following would work correctly:

echo "simply put,
just \"lend\" me US\$ $var" > a.config

answered Dec 20, 2012 at 13:46

scotjam1981

111 bronze badge

Comments

Hamid Reza · Accepted Answer · 2024-02-13 08:37:19Z

0

I would use tee command like this:

echo "My 
long
multiline
text
here!
" | sudo tee -a /etc/config.conf

answered Feb 13, 2024 at 8:37

Hamid Reza

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