Cannot rewrite some function from bash to nushell

Question

I'm moving from bash to nushell. One of my steps was moving this function:

ex ()
{
  if [ -f $1 ] ; then
    case $1 in
      *.tar.bz2)   tar xjf $1   ;;
      *.tar.gz)    tar xzf $1   ;;
      *.bz2)       bunzip2 $1   ;;
      *.rar)       unrar x $1     ;;
      *.gz)        gunzip $1    ;;
      *.tar)       tar xf $1    ;;
      *.tbz2)      tar xjf $1   ;;
      *.tgz)       tar xzf $1   ;;
      *.zip)       unzip $1     ;;
      *.Z)         uncompress $1;;
      *.7z)        7z x $1      ;;
      *)           echo "'$1' cannot be extracted via ex()" ;;
    esac
  else
    echo "'$1' is not a valid file"
  fi
}

In nushell I wrote this:

def ex [$file?: string] {
        if $file == null {"No file defined"} else {
                if $file == *.tar.bz2 {
                        tar xjf $file;
                }
                else if $file == *.tar.gz {
                        tar xzf $file;
                }
                else if $file == *.bz2 {
                        bunzip2 $file;
                }
                else if $file == *.rar {
                        unzip $file;
                }
                else if $file == *.gz {
                        gunzip $file;
                }
                else if $file == *.tar {
                        tar xf $file;
                }
                else if $file == *.tbz2 {
                        tar xjf $file;
                }
                else if $file == *.tgz {
                        tar xzf $file;
                }
                else if $file == *.zip {
                        unzip $file;
                }
                else if $file == *.Z {
                        uncompress $file;
                }
                else if $file == *.7z {
                        7z x $file;
                }
        }
}

But when I tested it by this command(I had an openssl source code archive in a directory I was executing command from): ex openssl-1.1.1.tar.gz, I got this error: `

ex openssl-1.1.1.tar.gz                                                                                          
Error: nu::shell::external_command (link)

  × External command failed
     ╭─[/home/ysyltbya/.config/nushell/config.nu:523:1]
 523 │          }
 524 │          else if $file == *.tar.gz {
     ·   ──┬─
     ·     ╰── did you mean 'ls'?
 525 │                  tar xzf $file;
     ╰────
  help: No such file or directory (os error 2)

I can't understand what the problem is.

NotTheDr01ds · Accepted Answer · 2022-11-25T20:22:57.727

The main issue is that you are still attempting to use the Bash patterns for string matching. You can accomplish this in Nushell with either:

The ends-with string comparison operator:
```
if $file ends-with '.tbz2' ...
```
Or a regex comparison:
```
if $file =~ '.*\.tbz2' ...
```

However, you might consider a more functional/data-driven/Nushell-way of doing it:

def ex [$file?: string] {
    let archivers = [
        [ pattern         , command              , options       ];
        [ ".tar.bz2"      , "tar"                , "xjf"         ]
        [ ".tar.gz"       , "tar"                , "xzf"         ]
        [ ".bz2"          , "unzip2"             , ""            ]
        [ ".tar.bz2"      , "tar"                , "xjf"         ]
        [ ".rar"          , "unrar"              , ""            ]
        [ ".gz"           , "gunzip"             , ""            ]
        [ ".tar"          , "tar"                , "xf"          ]
        [ ".tbz2"         , "tar"                , "xjf"         ]
        [ ".tgz"          , "tar"                , "xzf"         ]
        [ ".zip"          , "unzip"              , ""            ]
        [ ".Z"            , "uncompress"         , ""            ]
        [ ".7z"           , "7z"                 , "x"           ]
    ]

    if $file == null {
        print -e "No file defined"
    } else if not ($file | path exists) {
        print -e $"Can't find ($file)"
    } else {
        let matchingArchivers = ($archivers | where { |archiver| $file ends-with $archiver.pattern })
        if ($matchingArchivers | length) > 0 {
            let archiver = $matchingArchivers.0
            run-external $archiver.command $archiver.options $file
        } else {
            print -e $"($file) cannot be extracted via ex\(\)"
        }
    }
}

Notes:

Using this form, it's far easier to make changes and additions; more like the case of Bash in this sense.
I added in the other missing logic that you had like (a) checking that the file exists, and (b) checking that there was a matching app
Fixed the unzip command being used on rar files. Probably introduced some other transcription error in the process myself!
Yes, it does filter based on every possible match, rather than the normal "short-circuit" behavior of a case or if/else, but it's minimal impact.
Uses the first match found to mimic the behavior of case/if/else.

Cannot rewrite some function from bash to nushell

1 Answers1