Question

We (the company I work for) need to run the find2perl script on over a thousand different Unix servers of different flavors (Linux, Solaris, HP-UX, AIX) and different versions.

The one thing that all the servers have in common, is that they all have at least one implementation of perl installed. However, not all systems have it configured the same way.

Finding the location of perl is easy enough using the which command. However, on 70% of the servers, the actual directory containing find2perl (the bin folder of perl) is not present in the $PATH variable and can’t be located that way.

On some servers, perl is actually a symbolic link pointing another location, in which case I can use ls -l and sed to extract the target of the link to find where perl is actually installed.

On other servers however, it’s more complicated, as it seems perl was compiled to a custom location and the binary of perl present in /bin or /usr/bin (or wherever perl is found) is not a symbolic link, but rather a full blown executable. In this case, I thought about using the @INC variable of perl to try to find find2perl but it seems rather excessive.

What would be the better/best/fullproof method (one-liner if possible) to always get the location of find2perl on a Unix system?

Answer 1

Ways to locate find2perl

Two ways, both of which rely on asking the perl install how it was configured:

Config.pm

Its probably scriptdirexp from Config.pm.

$ perl -MConfig -E 'say $Config{scriptdirexp}'
/usr/bin

And indeed, that’s where find2perl is on my system. You can use Config; in your perl scripts, which is its major advantage over the next method.

perl -V:varname

As per Yanick Girouard’s comment, you can also use perl -V:scriptdirexp to get this, in a format suitable to passing to eval in a shell script. There are actually several formats available (so, you don’t need to use e.g., cut to parse it):

OPTION                 OUTPUT (\n = actual newline)     NOTES
-V:scriptdirexp        scriptdirexp='/usr/bin';\n       full shell syntax, even if multiple -V options
-V:scriptdirexp:       scriptdirexp='/usr/bin'          trailing colon omits semicolon and newline 
-V::scriptdirexp       '/usr/bin'; \n                   extra leading colon omits var= part
-V::scriptdirexp:      '/usr/bin'                       you can combine them.

Full documentation is in the perlrun manpage.

Ways to embed find2perl

If you decide to copy over find2perl, as per evil otto’s comment, you can actually do that by embedding it in your shell script. There are many ways. If neither of the two below work, then you can certainly use shar (which has an extremely long history, and is likely compatible with everything).

Quoted here-document

The easiest way is if your shell supports quoted here-documents. They all should, as its a POSIX requirement:

#!/bin/sh
perl - -name 'foo' -mtime 2 -print <<'FIND2PERL'
#!/usr/bin/perl
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
      if $running_under_some_shell;
⋮
FIND2PERL

Hex dump in a non-quoted here-document

If some of your shells don’t implement quoted here-documents (POSIX‽ what’s that!), then you have to protect find2perl from shell expansion. An easy way is to hex dump it, as 0–9 and a–f are all safe from shell expansion. The dump is easily done with xxd -p /usr/bin/find2perl, which only requires xxd on one machine. To read back the dump, you can use plain perl:

#!/bin/sh
perl -n -e 'chomp; print pack("H*", $_)' <<HEX | perl - -name 'foo'
23212f7573722f62696e2f7065726c0a202020206576616c202765786563
202f7573722f62696e2f7065726c202d5320243020247b312b222440227d
⋮
HEX

Using find2perl several times

Naturally, with either approach, you could also write find2perl to a temporary file (if you need to invoke it multiple times, for example). You could also embed it in a shell function.