EDIT 2: After learning that aliases aren’t really suited for regex, and trying the script, I thought maybe reloading the .bashrc file wasn’t enough to refresh the aliases, so I closed my terminal and after reopening the terminal and trying the script again it works just fine.

Okay, I’ve tried searching for help on this and I can’t find anything, and I’m banging my head on my desk trying to figure out how to get this to work.

I routinely have to capitalize the first letter in a series of files that are passed to me. So I’ll get:

file01
file02

And so on. I use perl rename (I’m using Fedora) with the following command and regex, and from within the directory it works as expected:

prename 's/(^[a-z]?)/\U$1/' *

I do this a lot. At least once a day, which calls for an alias or script.

I tried adding it as an alias to my .bash_aliases like so:

alias cap="prename 's/(^[a-z]?)/\U$1/' *"

And when I do, instead of capitalizing the first letter of the filenames it removes them. Searching got me nothing, in part because I probably am not asking the right question.

So then thought I’d write a dead simple bash script named cap (after removing the alias and reloading .bashrc)

#! /bin/bash

prename 's/(^[a-z]?)/\U$1/' *

And when I use cap in the directory, the script also cuts off the first letter instead of capitalizing it.

I suspect it’s the $1 variable in the regex that’s causing the problem, but I can’t figure out how to address it so it works correctly in the alias or the script.

EDIT: I just tried some more searching and found that regex won’t work in aliases, so it explains that, but I still can’t figure out how to get it to work in the script.

  • _edge@discuss.tchncs.de
    2·
    21 days ago

    Your problem is most likely escaping. $1 has a meaning in regex and in shell. You want the former and the single quotes achieve this.

    In your second example, with alias, probably the shell interpreting this replaces $1 with whatever the first arg in the shell environment is, probably the empty string.

    Not sure what the problem with the shell script is. Anyway try escaping the $ as $ and \ as \.

    You can see where you are wrong if you replace prename with echo for debugging. Or in a shell script do

    set -ex

  • huf [he/him]@hexbear.netEnglish
    3·
    21 days ago

    when you create the alias, the shell substitutes the $1 (to nothing, probably) since your alias is in "" (double quotes).
    now, if you swap the single and double quotes, then the substitution still happens, but at invocation time instead of at definition time.
    you actually want perl to deal with this $1, so neither is good.

    you have three options:

    • write a function instead, as has been suggested
    • use $'' quoting, which lets you put ’ (single quote) inside ’ (single quote) without going mad: alias cica=$'foo \'$bar\' baz'
    • go insane and do this: alias cica='foo '\''$bar'\'' baz' (this is the old way, without bash’s $'')
    • huf [he/him]@hexbear.netEnglish
      2·
      21 days ago

      i’d probably do

      function cap() {
        prename 's/(^[a-z]?)/\U$1/' "$@"
}

      it means it has to be invoked as cap *, but it also means that you can do cap foo* or whatever