Escape characters from echo -e

Question

I have the following in my .bashrc file I use for a log:

function log(){

  RED="\e[0;31m"
  RESET="\e[0m"
  echo -e "${RED}$(date)" "${RESET}$*" >> "$HOME"/mylog.txt
}

But when I do something with an apostrophe in it, it comes up with some sort of prompt and does not log it properly.

How do I escape all the text being input into the file?

Example:

$ log this is a testing's post
> hello
> 
> ^C
$

Thanks.

Answer 1

The problem you have has nothing to do with echo -e or your log() function. The problem is with apostrophes:

log this is a testing's post

The shell (bash, in your case) has special meanings for certain characters. Apostrophes (single quotes) are used to quote entire strings, and prevent most other kinds of interpolation. bash expects them to come in pairs, which is why you get the extra prompt lines until you type the second one. If you want a literal single quote in your string, you need to tell bash, by escaping it via \', like so:

log this is a testing\'s post

Again, log is beside the point. You can try this out with plain old echo if you like:

echo this is a testing\'s post

See Which characters need to be escaped in bash for more info.

Answer 2

Your problem is because you entered a command line that contained an unmatched single-quote character. It has nothing to do with echo. The shell is issuing a secondary prompt to let you know that it is expecting the end of the single-quoted string started by 's po...

You'd need to escape that ' if you want it passed litterally to the log function:

log "this is a testing's post"

Or:

log this is a testing\'s post

for instance.

Now, where you'd need to escape characters from echo -e is for the backslash characters. As for instance if you call it as log '\begin', that \b would be translated to a BS character by echo -e.

To address that, either store the escape sequences with those \e expanded in those variables:

log() {
  RED=$'\e[0;31m'
  RESET=$'\e[0m'
  printf '%s\n' "${RED}$(date) ${RESET}$*" >> "$HOME"/mylog.txt
}

(here using bash, ksh93, mksh, zsh or FreeBSD sh syntax for that not-yet-POSIX $'...' syntax).

Or use this syntax:

log() {
  RED='\e[0;31m'
  RESET='\e[0m'
  printf '%b%s%b %s\n' "$RED" "$(date)" "$RESET" "$*" >> "$HOME"/mylog.txt
}

Note that the expansion of "$*" depends on the current value of $IFS.

In any case, it's better to avoid echo for arbitrary data.