NAME

pl-canned-commands - Perl One-Liner Canned Commands

CANNED COMMANDS

If canned goods expire, are they canned bads? (-:

It's nice to have so many https://metacpan.org/dist/App-pl/view/pod/examples.pod, but copying some of the more frequently used ones in time of need would be cumbersome. Luckily there are better ways.

Let's explore two ways to make them more accessible from the Shell. You can put these in one of your Shell startup files like .bashrc to have them permanently available. The first, more compact but also limited, way is with aliases. The second, more flexible and powerful, way is with functions. However, depending on how flexible you want them to be, they require more or less Shell programming know how.

Shell Aliases

That smart pig's alias is Mr. Cunning Ham. :)

Right in the spirit of one-liners are Shell aliases. These have drawbacks:

• You will usually need to quote them. If you pass in Perl code containing dollar signs, you should single quote them to protect them from the Shell when running and yet again to protect them from the Shell when defining the alias.

• Their value literally replaces that one word at the beginning of a command. You can add arguments only at the end.

• Your IDE might not give you syntax highlighting for the value.

Either you can alias just initial options you use frequently. In that case you'd give some Perl code when invoking the alias, e.g., here to process the output of find:

    alias pl0='pl -nl0'
    find -type f -print0 |
        pl0 '...'

Or you alias a full command, in which case the Shell passes only the run-time arguments in @A(RGV). Since there are no dollars it doesn't matter which quote type you embed within the other:

    alias hosts="pl 'hosts @ARGV'"
    alias h="pl 'h @A'"

Here's an unnecessarily complex example where both the inner and outer strings need single quoting. We clumsily achieve that by leaving the outer single quoted string, appending a backslashed single quote and reentering the single quote again. Possible but a function would have been more readable here:

    alias whereis='pl '\''$p = $ENV{PATH} =~ s!/*:!,!gr;
        @x = grep { -f && -x } map <{$p}/$_>, @ARGV;
        exec ls => -fl => @x if @x'\'
    alias whereis='pl '\''$p = $ENV{PATH} =~ s!/*:!,!gr;
        @x = grep { -f && -x } map <{$p}/$_>, @A;
        exec ls => -fl => @x if @x'\'

Here are a few of the key-based diff examples. The 3rd name is unfortunate, as CSV commonly means "comma separated values," so "c" for "colon" was taken. That name might not work in all Shells, in which case you could use diffCsv:

    alias diffcsv="pl -nB 'echo for @ARGV' 'k if s/(.+?),//'"
    alias difftsv="pl -nB 'echo for @ARGV' 'k if s/(.+?)\t//'"
    alias diff:sv="pl -nB 'echo for @ARGV' 'k if s/^([^#].*?)://'"
    alias diffelf='pl -OB "echo for @ARGV" '\''p { k $2 if s/^\t((.+)\.so.* => .*) \(\w+\)/$1/ } ldd => $ARGV'\'
    alias diffcsv="pl -nB 'e for @A' 'k if s/(.+?),//'"
    alias difftsv="pl -nB 'e for @A' 'k if s/(.+?)\t//'"
    alias diff:sv="pl -nB 'e for @A' 'k if s/^([^#].*?)://'"
    alias diffelf='pl -OB "e for @A" '\''p { k $2 if s/^\t((.+)\.so.* => .*) \(\w+\)/$1/ } ldd => $A'\'

We can import some of the pl functionality directly to the Shell. My favourite is the smart e(cho), only by short name to avoid collision. Shell meta-characters like * need quoting. I chose to treat multiple arguments as though they were one, therefore needing a comma if I have more than one expression. Since the expression needs eval I can even have multiple statements, the last one being the list that e(cho) sees:

    alias e="pl 'e eval qq{@A}; die \$@ if \$@'"
    e 10 / 3, '7 * 3'
    e '$x = 5; 10 / $x, $x * 2'

    >   3.33333333333333 21
    >   2 10

Template has a prototype, for the 1st argument to default to $_. This is how to still pass all alias arguments as a list:

    alias template="pl '&template( @ARGV )'"
    template "Don't {{verb}} the {{noun}}, make the {{noun}} {{verb}}!" verb count noun days
    alias t="pl '&t( @A )'"
    t "Don't {{verb}} the {{noun}}, make the {{noun}} {{verb}}!" verb count noun days

    >   Don't count the days, make the days count!

On the Shell, you may be more interested in reading from a file, whose name shall get passed backslashed as a ref (multiply, because of "):

    alias Template="pl -B '\$file = shift' '&Template( \\\$file, @ARGV )'"
    Template filename key value ...
    alias T="pl -B '\$file = shift' '&T( \\\$file, @A )'"
    T filename key value ...

Shell Functions

I can't function without my glasses. Especially when they're empty! 8-)

Functions (here using the classical syntax understood by various Shells) directly contain normal Shell code. They avoid the double quoting problem of aliases. In the simplest case, you just wrap any pl command like this, with a special sigil meaning pass the function's parameters to pl here:

    somename() {
        pl ... "$@"
    }

You can jazz up some more key-based diff examples as functions. That way we can have options, like -d for "eliminate date" or for zip -x for "extract hex part of filename."

    diffzip() {
        local prg='if s/ [0-9a-f]{8}\K  (.+)//'
        if [ "x$1" = x-x ]; then        # randomized hex web resource
            shift
            prg='$n if s/.{16} ([0-9a-f]{8})  (.+?)(?:\.([0-9a-f]{20})(\..[a-z]+))?$/if( $3 ) { $n = "$2.\$x$4"; "$1  \$x=$3" } else { $n = $2; $1 }/e'
        elif [ "x$1" = x-d ]; then      # dateless
            shift
            prg='$2 if s/.{16} ([0-9a-f]{8})  (.+)/$1/'
        fi
        pl -oB 'echo for @ARGV' 'piped { keydiff '"$prg"' } "unzip", "-vqq", $_' "$@"
    }
    difftar() {
        local prg='s/^\S+ \K(.+?) +(\d+) (.{16}) (.+)/sprintf "%-20s %10d %s", $1, $2, $3/e; keydiff $4'
        if [ "x$1" = x-d ]; then      # dateless
            shift
            prg='s/^\S+ \K(.+?) +(\d+) .{16} (.+)/sprintf "%-20s %10d", $1, $2/e; keydiff $3'
        fi
        pl -oB 'echo for @ARGV' 'piped { '"$prg"' } "tar", "-tvf", $_' "$@"
    }    diffzip() {
        local prg='if s/ [0-9a-f]{8}\K  (.+)//'
        if [ "x$1" = x-x ]; then        # randomized hex web resource
            shift
            prg='$n if s/.{16} ([0-9a-f]{8})  (.+?)(?:\.([0-9a-f]{20})(\..[a-z]+))?$/if( $3 ) { $n = "$2.\$x$4"; "$1  \$x=$3" } else { $n = $2; $1 }/e'
        elif [ "x$1" = x-d ]; then      # dateless
            shift
            prg='$2 if s/.{16} ([0-9a-f]{8})  (.+)/$1/'
        fi
        pl -oB 'e for @A' 'p { k '"$prg"' } "unzip", "-vqq", $_' "$@"
    }
    difftar() {
        local prg='s/^\S+ \K(.+?) +(\d+) (.{16}) (.+)/sprintf "%-20s %10d %s", $1, $2, $3/e; k $4'
        if [ "x$1" = x-d ]; then      # dateless
            shift
            prg='s/^\S+ \K(.+?) +(\d+) .{16} (.+)/sprintf "%-20s %10d", $1, $2/e; k $3'
        fi
        pl -oB 'e for @A' 'p { '"$prg"' } "tar", "-tvf", $_' "$@"
    }