Bash Input/Output

Internal

• bash

Echo Multiple Lines to stdout

cat <<EOF
  blah
  ${some_var}
  blah
EOF

• It will perform variable substitution. If you don't want that, escape \${some_var}.
• `...` sequences should be escaped as shown here: \`...\` otherwise they will executed before the output is sent to stdout.
• \ will join lines. If you want "\" in the output, then you should escape it:

      ...
      blah blah \\
      ...

Echo Multiple Lines into a File

(cat << EOF
blah
EOF
) > /tmp/test.txt

Iterating over Lines in the Same bash Process

With for

Iterating over Lines in the Same bash Process

Extracting a Line Specified by Its Number from a File

With head and tail

Extract line 15 (line numbers are 1-based):

cat ./test.txt | head -15 | tail -1

With sed

Print a Line Specified by Its Number with sed