How to use shell variables in perl command call in

问题:

How to use shell variables in perl command call in a bash shell script?

I have a perl command in my shell script to evaluate date -1.

How can i use $myDate in perl command call?

This is the section in my script:

myDate='10/10/2012'

Dt=$(perl -e 'use POSIX;print strftime '%m/%d/%y', localtime time-86400;")

I want use $myDate in place of %m/%d/%y.

Any help will be appreciated.

Thank you.

回答1:

The same way you pass values to any other program: Pass it as an arg. (You might be tempted to generate Perl code, but that's a bad idea.)

Dt=$( perl -MPOSIX -e'print strftime $ARGV[0], localtime time-86400;' -- "$myDate" )

Note that code doesn't always return yesterday's date (since not all days have 86400 seconds). For that, you'd want

Dt=$( perl -MPOSIX -e'my @d = localtime time-86400; --$d[4]; print strftime $ARGV[0], @d;' -- "$myDate" )

or

Dt=$( perl -MDateTime -e'print DateTime->today(time_zone => "local")->subtract(days => 1)->strftime($ARGV[0]);' -- "$myDate" )

or simply

Dt=$( date --date='1 day ago' +"$myDate" )

回答2:

Variables from the shell are available in Perl's %ENV hash. With bash (and some other shells) you need to take the extra step of "exporting" your shell variable so it is visible to subprocesses.

mydate=10/10/2012
export mydate
perl -e 'print "my date is $ENV{mydate}\n"'

回答3:

Using " instead of ' also passes shell variables to perl in version 5.24.

mydate=22/6/2016
perl -e "print $mydate"

回答4:

The same way you pass values to any other program: Pass it as an arg. (You might be tempted to generate Perl code, but that's a bad idea.)

Dt=$( perl -MPOSIX -e'my($m,$d,$y) = split qr{/}, $ARGV[0]; --$d; print strftime "%m/%d/%y", 0,0,0, $d,$m-1,$y-1900;' -- "$myDate" )

回答5:

Why not something like: $ENV{'PATH'} = $ENV{'PATH'}.":"."/additional/path";

回答6:

For me, I need to use $ENV{'VARIABLE'} to pass VARIABLE in shell to Perl. I do not know why simply $ENV{VARIABLE} did not work.

For example,

In Bash:

#!/bin/bash -l
VARIABLE=1
export VARIABLE
perl example.pl

In Perl:

#!/usr/bin/perl -w
print "my number is " . $ENV{'VARIABLE'}