Can I feed a bash script a local file into $1 and have it echo the file's absolute path? [duplicate]

Script is not necessary. A single readlink command is sufficient:

$ cd /etc/

$ readlink -e passwd
/etc/passwd

From the man readlink:

   -e, --canonicalize-existing
          canonicalize by following every symlink in every component
          of the given name recursively, all components must exist

If your script is

#!/bin/bash
[[ -e "$1" ]] && readlink -f -- "$1"

And has execute permission (chmod u+x scriptname) You can enter

./scriptname file

To get the full path if the file exists (although Serg is right that the test is redundant if we use readlink -e and George is right to use realpath rather than readlink)

Notes

• [[ -e "$1" ]] test whether $1, the first argument to the script, exists
• && if it does (if the previous command was successful) then do the next command
• readlink -f -- "$1" print the full path (to the real file, even if $1 is a symlink)

OP requested special characters be printed with escapes. There must be a smart way* but I did it like this (although it won't deal with single quotes - but those cannot be escaped anyway)

[[ -e "$1" ]] && readlink -f -- "$1" | sed -r 's/\||\[|\]| |!|"|\$|%|\^|&|\*|\(|\)\{|\}|\#|@|\;|\?|<|>/\\&/g'

If it's only spaces you're worried about, you could make that

sed 's/ /\\ /g'

This would get single quotes (not very usefully) and spaces

sed -r "s/'| /\\\&/g"

But I don't think you can catch both single quotes and double quotes...

* Here's the smart way, 100% credit to steeldriver

[[ -e "$1" ]] && printf "%q\n" "$(readlink -f -- "$1")"

#!/bin/bash

[[ -e "$1" ]] && echo realpath -e "$1"

Update to take care of non-alphanumeric characters:

#!/bin/bash

[[ -e "$1" ]] && echo "$1" | sed -r 's/[^a-zA-Z0-9\-]/\//g' | realpath -e "$1"

Prepare script: chmod +x script_name, then

use it : ./script_name filename

Information:

1. [[ -e "$1" ]]: check if the passed file exists.