How can I write multi-lines in a file called myconfig.conf using BASH?
#!/bin/bash
kernel="2.6.39";
distro="xyz";
echo <<< EOL
line 1, ${kernel}
line 2,
line 3, ${distro}
line 4
line ...
EOL >> /etc/myconfig.conf;
cat /etc/myconfig.conf;
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9 Answers
The syntax (<<<) and the command used (echo) is wrong.
Correct would be:
#!/bin/bash
kernel="2.6.39"
distro="xyz"
cat >/etc/myconfig.conf <<EOL
line 1, ${kernel}
line 2,
line 3, ${distro}
line 4 line
...
EOL
cat /etc/myconfig.conf
This construction is referred to as a Here Document and can be found in the Bash man pages under man --pager='less -p "\s*Here Documents"' bash.
13 Comments
Or Gal
and if you want to append it would be cat >>
nwinkler
This works great, but you have to make sure that there's no whitespace in front of the terminating
EOF, otherwise it will not be recognized, and you will run into an unexpected end of file error.
William Pursell
@StevenEckhoff This is called a heredoc.
gfpacheco
What if I need sudo permission to write to the file?
Xin Chen
@gfpacheco You can use tee for that, like cat << EOL | sudo tee /etc/myconfig.conf
|
#!/bin/bash
kernel="2.6.39";
distro="xyz";
cat > /etc/myconfig.conf << EOL
line 1, ${kernel}
line 2,
line 3, ${distro}
line 4
line ...
EOL
this does what you want.
3 Comments
Kent
@ktf I was typing not faster, but less letters than you. ^_*
Milad Yarmohammadi
You were faster but its not enough :))))
Vibhanshu Biswas
This helped a lot!
If you do not want variables to be replaced, you need to surround EOL with single quotes.
cat >/tmp/myconfig.conf <<'EOL'
line 1, ${kernel}
line 2,
line 3, ${distro}
line 4 line
...
EOL
Previous example:
$ cat /tmp/myconfig.conf
line 1, ${kernel}
line 2,
line 3, ${distro}
line 4 line
...
1 Comment
Yevhen Tienkaiev
Thanks for nuance when I don't wanna modify variables. e.g. having it in quotes
'EOL'The heredoc solutions are certainly the most common way to do this. Other common solutions are:
echo 'line 1, '"${kernel}"'
line 2,
line 3, '"${distro}"'
line 4' > /etc/myconfig.conf
and
exec 3>&1 # Save current stdout
exec > /etc/myconfig.conf
echo line 1, ${kernel}
echo line 2,
echo line 3, ${distro}
...
exec 1>&3 # Restore stdout
and
printf "%s\n" "line1, ${kernel}" "line2," "line3, $distro" ...
1 Comment
tripleee
Maybe also point to
printf which introduces yet some more interesting variations.I'm using Mac OS and to write multiple lines in a SH Script following code worked for me
#! /bin/bash
FILE_NAME="SomeRandomFile"
touch $FILE_NAME
echo """I wrote all
the
stuff
here.
And to access a variable we can use
$FILE_NAME
""" >> $FILE_NAME
cat $FILE_NAME
Please don't forget to assign chmod as required to the script file. I have used
chmod u+x myScriptFile.sh
Comments
Below mechanism helps in redirecting multiple lines to file. Keep complete string under " so that we can redirect values of the variable.
#!/bin/bash
kernel="2.6.39"
echo "line 1, ${kernel}
line 2," > a.txt
echo 'line 2, ${kernel}
line 2,' > b.txt
Content of a.txt is
line 1, 2.6.39
line 2,
Content of b.txt is
line 2, ${kernel}
line 2,
Comments
In my usecase I had to use the following:
{
...
printf "Suites: $SUITES"
printf "Components: $COMPONENTS"
printf "Signed-By: $SIGNATURE"
[ ! -z "$ARCH_STRING" ] && printf "$ARCH_STRING"
[ ! -z "$LANG_STRING" ] && printf "$LANG_STRING"
[ ! -z "$TARGET_STRING" ] && printf "$TARGET_STRING"
...
} > /tmp/myconfig.conf
This because I did not want to write empty newlines to the file if the variables were not defined. The nice thing about this method is that you can write all kinds of arbitrary logic within the block if necessary.
And ofcourse, if you would like to append, you can also use >> here instead of > like you would in the other answers.
Comments
I usually put template in file and use this templating engine:
### <template-file> [ARG=VALUE..]
## Variables are replaced only within "{{" and "}}" notation.
## Example:
## $0 path-to-tmpl REF=master pass=xx
## # The template may look like so:
## # $pass = ["user", "{{ $pass }}"];
## # Resulting in:
## # $pass = ["user", "xxx"];
##~
template() {
tmpl=$1
shift
for i in $@; do
declare $i;
done
eval "echo \"$(sed -e 's/"/\\"/g' -e 's/\$/\\$/g' -e 's/{{\s*\\\(\$\w*\)\s*}}/\1/g' $tmpl)\""
}
Comments
another simpler way I think but definitely for small number of lines
touch myfile.txt
echo "line1">>myfile.txt
echo "line2">>myfile.txt
echo "line3">>myfile.txt
echo "line4">>myfile.txt
