How can I print a newline as \n in bash?

If your input is already in a (bash) shell variable, say $varWithNewlines:

echo "${varWithNewlines//$'\n'/\\n}"

Simply uses bash parameter expansion to replace all newline ($'\n') instances with literal '\n' each.

If your input comes from a file, use awk:

awk -v ORS='\\n' 1

In action, with sample input:

# Sample input with actual newlines created with ANSI C quoting ($'...'), 
# which turns `\n` literals into actual newlines.
varWithNewlines=$'line 1\nline 2\nline 3'

# Translate newlines to '\n' literals.
# Note the use of `printf %s` to avoid adding an additional newline.
# By contrast, a here-string - <<<"$varWithNewlines" _always appends a newline_.
printf %s "$varWithNewlines" | awk -v ORS='\\n' 1
  • awk reads input line by line
  • by setting ORS- the output record separator to literal '\n' (escaped with an additional \ so that awk doesn't interpret it as an escape sequence), the input lines are output with that separator
  • 1 is just shorthand for {print}, i.e., all input lines are printed, terminated by ORS.

Note: The output will always end in literal '\n', even if your input does not end in a newline.
This is because awk terminates every output line with ORS, whether the input line ended with a newline (separator specified in FS) or not.

Here's how to unconditionally strip the terminating literal '\n' from your output.

# Translate newlines to '\n' literals and capture in variable.
varEncoded=$(printf %s "$varWithNewlines" | awk -v ORS='\\n' 1)

# Strip terminating '\n' literal from the variable value 
# using bash parameter expansion.
echo "${varEncoded%\\n}"

By contrast, more work is needed if you want to make the presence of a terminating literal '\n' dependent on whether the input ends with a newline or not.

# Translate newlines to '\n' literals and capture in variable.
varEncoded=$(printf %s "$varWithNewlines" | awk -v ORS='\\n' 1)

# If the input does not end with a newline, strip the terminating '\n' literal.
if [[ $varWithNewlines != *$'\n' ]]; then 
  # Strip terminating '\n' literal from the variable value 
  # using bash parameter expansion.
  echo "${varEncoded%\\n}"
else 
  echo "$varEncoded"
fi

Here's my solution:

sed 's/$/\\n/' | tr -d '\n'

Tags:

Shell

Bash

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