user-tools/substenv

   1 #!/usr/bin/env perl
   2
   3 =pod
   4
   5 =head1 NAME
   6
   7 substenv - Substitute environment variables in parameters and run the resulting command
   8
   9 =head1 SYNOPSIS
  10
  11 substenv I<COMMAND> [I<ARGS>]
  12
  13 =head1 DESCRIPTION
  14
  15 Replace all occurrances of C<$NAME> in I<COMMAND> and I<ARGS> to the I<NAME> environment
  16 variable's value, then run I<COMMAND>.
  17
  18 =head1 EXAMPLE
  19
  20 This function call, in C, runs substenv(1),
  21 note, there is no dollar-interpolation in C.
  22
  23  execve("substenv", ["substenv", "ls", "$HOME/.config"])
  24
  25 Then substenv issues this system call:
  26
  27  execve("ls", ["ls", "/home/jdoe/.config"])
  28
  29 =head1 NOTES
  30
  31 Does not support full shell-like variable interpolation.
  32 Use a real shell for it.
  33
  34 =head1 RATIONALE
  35
  36 Sometimes you don't want a shell to be in the picture when composing commands,
  37 yet need to weave some environment variable into it.
  38
  39 =head1 SEE ALSO
  40
  41 envsubst(1) from gettext-base package
  42
  43 =cut
  44
  45
  46 @run_cmd = ();
  47
  48 for my $arg (@ARGV)
  49 {
  50         $arg =~ s/\$([A-Z0-9_]+)/$ENV{$1}/g;
  51         push @run_cmd, $arg;
  52 }
  53
  54 exec {$run_cmd[0]} @run_cmd;
  55 ($errno, $errstr) = (int $!, $!);
  56 warn "$0: ${run_cmd[0]}: $errstr\n";
  57 exit 125+$errno;