Clavin June

Posted on Jan 13, 2022 • Originally published at clavinjune.dev on Jan 13, 2022

Unix Heredoc Cheatsheet

Clavin June · 2022-01-13T03:56:39Z

Syntax [ cmd] << [ -] delimeter [ cmd] contents delimeter Enter fullscreen mode Exit fullscreen mode All contents will be passed to the cmd as an input, examples below will use EOF as a delimeter and cat as a command, you can change to whatever you want. With Variable cat << EOF echo " $HOME " EOF Enter fullscreen mode Exit fullscreen mode result: echo "/home/clavinjune" Enter fullscreen mode Exit fullscreen mode Escape Variable Use \$ instead of $ to escape specific variable cat << EOF echo " $HOME " echo " \$ HOME" EOF Enter fullscreen mode Exit fullscreen mode result: echo "/home/clavinjune" echo " $HOME " Enter fullscreen mode Exit fullscreen mode Escape All Variables Use 'EOF' instead of EOF to escape all variables cat << ' EOF ' echo " $HOME " echo " \$ HOME" EOF Enter fullscreen mode Exit fullscreen mode result: echo " $HOME " echo " \$ HOME" Enter fullscreen mode Exit fullscreen mode Remove Leading Tab Use <<- instead of << to remove leading tabs cat <<- EOF echo " $HOME " echo " \$ HOME" EOF Enter fullscreen mode Exit fullscreen mode result: echo "/home/clavinjune" echo " $HOME " Enter fullscreen mode Exit fullscreen mode Add More Pipeline cat << EOF | grep june echo " $HOME " echo " \$ HOME" EOF Enter fullscreen mode Exit fullscreen mode result: echo "/home/clavinjune" Enter fullscreen mode Exit fullscreen mode Write To a File cat <<- ' EOF ' > /tmp/foo echo " $HOME " echo " \$ HOME" EOF Enter fullscreen mode Exit fullscreen mode result: $ cat /tmp/foo echo " $HOME " echo " \$ HOME" Enter fullscreen mode Exit fullscreen mode Thank you for reading!

#unix #beginners #linux #shell

Syntax

[cmd] <<[-] delimeter [cmd]
    contents
delimeter

All contents will be passed to the cmd as an input, examples below will use EOF as a delimeter and cat as a command, you can change to whatever you want.

With Variable

cat <<EOF
    echo "$HOME"
EOF

result:

    echo "/home/clavinjune"

Escape Variable

Use \$ instead of $ to escape specific variable

cat <<EOF
    echo "$HOME"
    echo "\$HOME"
EOF

result:

    echo "/home/clavinjune"
    echo "$HOME"

Escape All Variables

Use 'EOF' instead of EOF to escape all variables

cat <<'EOF'
    echo "$HOME"
    echo "\$HOME"
EOF

result:

    echo "$HOME"
    echo "\$HOME"

Remove Leading Tab

Use <<- instead of << to remove leading tabs

cat <<-EOF
    echo "$HOME"
    echo "\$HOME"
EOF

result:

echo "/home/clavinjune"
echo "$HOME"

Add More Pipeline

cat <<EOF | grep june
    echo "$HOME"
    echo "\$HOME"
EOF

result:

    echo "/home/clavinjune"

Write To a File

cat <<-'EOF' > /tmp/foo
    echo "$HOME"
    echo "\$HOME"
EOF

result:

$ cat /tmp/foo 
echo "$HOME"
echo "\$HOME"

Thank you for reading!

Top comments (1)

andywu1998 • Jan 18 '22

so nice, thanks for sharing. expect to update~