ln command breaks when there is a space in filename

Question

#!/bin/bash
for i in instances/*; do
        #echo $i
        if [[ -d "${i}/.minecraft/" ]]; then
                echo "${i}/.minecraft/"
                if [ -h "${i}/.minecraft/saves" ]; then
                        rm -f "${i}/.minecraft/saves"
                else rm -rf   "${i}/.minecraft/saves";
                fi
                ln -s saves '"'${i}/.minecraft/saves'"'
        fi
done

this is my script for linking up the saves in my PolyMC setup. the problem is that the code doesnt work if DIRECTORY has a space:

instances/1.19 Sodium/.minecraft/ this has the following output:

ln: target 'Sodium/.minecraft/saves"': No such file or directory

also removing '"' still has the same error

`'"'` What are you tring to do with this? Just use `"${i}/.minecraft/saves"`. — tkausl, Jul 16 '22 at 12:42
You aren't quoting the parameter expansion; you're trying to add quotes to the *results* of the expansion. — chepner, Jul 16 '22 at 12:47
Why are you quoting the `ln` arguments differently from the `echo` and `rm` arguments? — Jens, Jul 16 '22 at 13:12
@tkausl its a cool hack i found that fixed an ffmpeg automation script — PranshuTheGamer, Jul 16 '22 at 15:12
Its not a _cool hack_, it was put there for a purpose and that purpose doesn't apply to your code, so don't use it. — tkausl, Jul 16 '22 at 15:13
it wont work without it either. also what is does is it passes on the double qoute, which i have i found, helps when commands are sensitive to white spaces — PranshuTheGamer, Jul 16 '22 at 15:14
@tkausl can you suggest changes, removing `"'"` still gives the same error — PranshuTheGamer, Jul 16 '22 at 15:59

score 0 · Answer 1 · answered Jul 16 '22 at 22:47

As everyone already commented, it's not about removing the '"' but to quote your $i inside double quotes. Nor is it a random combination of " and ' to make it work.

Explanations :

When i contains a space like : i="1.19 Sodium" (here the double quotes are delimiters, not characters of the string),

the line ln -s saves '"'${i}/.minecraft/saves'"'

is seen as :

ln -s saves '"'1.19 Sodium/.minecraft/saves'"'

In this context, single quotes are string delimiters, while double quotes are any (unwanted) characters in the string.

It is read as :

The word ln,
A field separator,
The word -s,
A field separator,
The word saves,
A string (delimited by single quotes) of one character " concatenated to the word 1.19,
The space (coming from i) interpreted (since outside quotes) as a field separator,
The word Sodium/.minecraft/saves concatenated to a string (delimited by single quotes) of one character ".

Then it's exactly equivalent to : ln -s saves '"1.19' 'Sodium/.minecraft/saves"'

Which is not what you want, and why the error message says Sodium/.minecraft/saves" does not exist.

As @tkausl commented, the solution is "${i}/.minecraft/saves" (or without the braces "$i/.minecraft/saves").

With this, when i contains a space like : i="1.19 Sodium",

the line ln -s saves "$i/.minecraft/saves"

is seen as :

ln -s saves '1.19 Sodium/.minecraft/saves',
or (equivalent) ln -s saves "1.19 Sodium/.minecraft/saves",
or (equivalent) ln -s saves 1.19\ Sodium/.minecraft/saves.

With the correction, any space in i will no longer be interpreted as a field separator because i is in a string delimited by double quotes.

Conclusion: Never use non-quoted variables (even echo "$i" instead of echo $i).

Just to note, the single quotes are not string *delimiters*. They (and double quotes) are just a form of bulk escaping; every character inside the quotes is treated as if it were preceded by a backslash (with some exceptions inside double quotes). — chepner, Jul 16 '22 at 22:50
@chepner Yes I should have emphasized that it wasn't in a potential technical word sense that I was using it (I used italic for "field separator" only). I didn't know how else to say it in this context. Example of not string delimiters: `cmd0 "$(cmd1 "$var2")"` :-) — syme, Jul 16 '22 at 23:02

ln command breaks when there is a space in filename

1 Answers1