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Bash Escape Characters For example, if we have a multiline string in a script, we can use the \n character to create a new line where necessary. Executing the above script prints the strings in a new line where the \n character exists.
To add multiple lines to a file with echo, use the -e option and separate each line with \n. When you use the -e option, it tells echo to evaluate backslash characters such as \n for new line. If you cat the file, you will realize that each entry is added on a new line immediately after the existing content.
Use printf to Make Multi-Line String in Bash We can use printf with the new line character and redirect the output to a file using > . The content in the file does not have extra spaces.
Use triple quotes to create a multiline string It is the simplest method to let a long string split into different lines. You will need to enclose it with a pair of Triple quotes, one at the start and second in the end. Anything inside the enclosing Triple quotes will become part of one multiline string.
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.
#!/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.
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, ${distro}
line 4 line
...
The heredoc solutions are certainly the most common way to do this. Other common solutions are:
echo 'line 1, '"${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" ...
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,
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