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#++
# NAME
# command.pl 3p
# SUMMARY
# command plumbing
# SYNOPSIS
# require 'command.pl';
#
# $timeouts{$command} = $short_timeout;
#
# execute_command(@command)
#
# pipe_command($handle, @command, $mode)
#
# redirect_command(@command, $file)
#
# command_to_list(@command)
#
# command_to_string(@command)
# DESCRIPTION
# This module attempts to provide safe alternatives for running
# commands with or without I/O redirected to or from files or pipes,
# and for capturing the output from a command in a variable. In
# particular, commands are not parsed by a shell.
#
# Each command, and its method of I/O redirection, are logged to
# the logging module.
#
# Each command is logged to STDOUT if $verbose is set.
#
# Each command is subjected to a time limit as specified in the
# %timeouts hash. The default time limit is $short_timeout. For
# convenience, the coroner.cf file provides initial values of
# %timeouts, $short_timeout, $med_timeout and $long_timeout.
#
# execute_command() executes the command without performing any
# I/O redirection. The result is the command exit status.
#
# pipe_command() executes the command with its input or output
# redirected to or from the specified handle. The mode argument
# is either "|-" in order to write to the command, or "-|" in
# order to read from the command. The result is undef in case of
# problems, otherwise the result is the handle argument.
#
# redirect_command() executes the command with I/O redirection
# under control by the $file argument. In order to redirect
# input, specify "<filename"; in order to redirect output, specify
# ">filename" or ">>filename". The result is -1 when fork()
# was unable to create a process, the command exit status otherwise.
# The command exit status is also available as $?.
#
# command_to_list() executes the command and returns a list
# of output lines. The result is undef in case of problems.
# The command exit status is available as $?.
#
# command_to_string() executes the command and returns a string
# with the command output, including newlines. The result is undef
# in case of problems. The command exit status is available as $?.
# LICENSE
# This software is distributed under the IBM Public License.
# SEE ALSO
# timeout(1) run command with time limit
# AUTHOR(S)
# Wietse Venema
# IBM T.J. Watson Research
# P.O. Box 704, Yorktown Heights, NY 10598, USA
#--
require "logger.pl";
sub timed_exec
{
my(@command) = @_;
my($limit);
$limit = $short_timeout
unless $limit = $timeouts{$command[0]};
return (exec($TIMEOUT, $limit, @command));
}
# pipe_command($handle, @command, $mode) - run command, return handle
sub pipe_command
{
my($handle, @command) = @_;
my($mode) = pop(@command);
my($pid);
print "pipe_command: $handle @command $mode\n"
if $verbose;
die "pipe_command: invalid pipe mode: $mode\n"
unless ($mode eq "-|" || $mode eq "|-");
&log_item($mode eq "|-" ? "PIPETO_CMD" : "PIPEFROM_CMD", @command);
return(undef)
unless defined($pid = open($handle, $mode));
if ($pid == 0) {
&timed_exec(@command) || die "cannot exec $command[0]: $!\n";
exit 1;
} else {
return($handle);
}
}
# execute_command(@command) - run command, no I/O redirection
sub execute_command
{
my(@command) = @_;
my($pid);
print "execute_command: @command\n"
if $verbose;
&log_item("EXECUTE_CMD", @command);
if (($pid = fork()) == 0) {
&timed_exec(@command) || die "cannot exec $command[0]: $!\n";
exit 1;
} elsif ($pid == -1) {
return(-1);
} else {
waitpid($pid, 0);
return($?);
}
}
# redirect_command(@command, $file) - run command, redirected
sub redirect_command
{
my(@command) = @_;
my($file) = pop(@command);
my($pid);
print "redirect_command: @command $file\n"
if $verbose;
&log_item("REDIRECT_CMD", $file, @command);
if (($pid = fork()) == 0) {
if ($file =~ /^>/) {
open(STDOUT, $file) || die "cannot open $file: $!\n";
} elsif ($file =~ /^</) {
open(STDIN, $file) || die "cannot open $file: $!\n";
} else {
die "redirect_command: invalid I/O redirection: $file\n";
}
&timed_exec(@command) || die "cannot exec $command[0]: $!\n";
exit 1;
} elsif ($pid == -1) {
return(-1);
} else {
waitpid($pid, 0);
return($?);
}
}
# command_to_list(@command) - run command, output to list
sub command_to_list
{
my(@command) = @_;
my(@output);
my($pid);
print "command_to_list: @command\n"
if $verbose;
&log_item("PIPEFROM_CMD", @command);
return(undef)
unless defined($pid = open(COMMAND_TO_LIST, "-|"));
if ($pid == 0) {
&timed_exec(@command) || die "cannot exec $command[0]: $!\n";
exit 1;
} else {
@result = <COMMAND_TO_LIST>;
close(COMMAND_TO_LIST);
return(@result);
}
}
# command_to_string(@command) - run command, output to string
sub command_to_string
{
my(@command) = @_;
return(join('', &command_to_list(@command)));
}
1;
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