No::Worries::Proc(3pm)

1No::Worries::Proc(3)  User Contributed Perl Documentation No::Worries::Proc(3)
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NAME

6       No::Worries::Proc - process handling without worries
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SYNOPSIS

9         use No::Worries::Proc qw(proc_run proc_create proc_monitor proc_detach);
10
11         # simple interface to execute a command
12         $status = proc_run(command => [ "foo", "-x", 7 ]);
13         printf("foo exited with %d\n", $status);
14
15         # idem but with output redirection and more information
16         %proc = proc_run(command => [ qw(uname -a) ], stdout => \$output);
17         printf("process %d output is %s\n", $proc->{pid}, $output);
18
19         # start two process and wait for them to finish
20         $p1 = proc_create(
21             command => \@cmd1,
22             timeout => 5,           # to be killed if still running after 5s
23             stderr  => "/dev/null", # discard stderr
24         );
25         $p2 = proc_create(
26             command => \@cmd2,
27             stdout  => \$output,    # get stdout+stderr in $output
28             stderr  => "",          # merge stderr with stdout
29         );
30         proc_monitor([ $p1, $p2 ], timeout => 10);
31         printf("%d finished\n", $p1->{pid}) if $p1->{stop};
32         printf("%d finished\n", $p2->{pid}) if $p2->{stop};
33
34         # detach ourself to run as a daemon
35         proc_detach(callback => sub { print("started with pid $_[0]\n")});
36

DESCRIPTION

38       This module eases process handling by providing high level functions to
39       start, monitor and stop processes. All the functions die() on error.
40
41       It also provides the $No::Worries::Proc::Transient variable that
42       indicates, after a fork(), which process is transient and is about to
43       exec() or exit().  This is useful for instance in an END block:
44
45         END {
46             # remove our pid file unless we are transient
47             pf_unset($pidfile) unless $No::Worries::Proc::Transient;
48         }
49

FUNCTIONS

51       This module provides the following functions (none of them being
52       exported by default):
53
54       proc_output(COMMAND...)
55           execute the given command, capture its output (stdout only), check
56           its exit code (report an error if it is not zero) and return the
57           captured output; this is similar to Perl's qx() operator but
58           bypassing the shell and always checking the exit code
59
60       proc_create(OPTIONS)
61           create a new process that will execute the given command and return
62           a hash reference representing this process (see the "PROCESS
63           STRUCTURE" sections for more information), to be given to
64           proc_monitor() or proc_terminate() afterwards; supported options:
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66           ·   "command": the command to execute, it must be an array
67               reference
68
69           ·   "cwd": the current working directory of the new process
70
71           ·   "timeout": the maximum number of seconds that the process is
72               allowed to take to run (can be fractional); after this, it may
73               be killed by proc_monitor()
74
75           ·   "kill": how to "gently" kill the process, see below
76
77           ·   "stdin": what to do with stdin, see below
78
79           ·   "stdout": what to do with stdout, see below
80
81           ·   "stderr": what to do with stderr, see below
82
83       proc_terminate(PROC[, OPTIONS])
84           terminate the given process (PROC can be either a process structure
85           or simply a process id) by sending signals and waiting for the
86           process to finish; supported options:
87
88           ·   "kill": how to "gently" kill the process, see below
89
90       proc_monitor(PROCS[, OPTIONS])
91           monitor the given process(es) (as created by proc_create()); PROCS
92           can be either a single process or a reference to a list of
93           processes; supported options:
94
95           ·   "timeout": the maximum number of seconds that proc_monitor()
96               should take, can be fractional
97
98           ·   "bufsize": the buffer size to use for I/O operations (default:
99               8192)
100
101           ·   "deaths": the minimum number of process deaths that
102               proc_monitor() will wait for before returning
103
104       proc_run(OPTIONS)
105           execute the given process (i.e. create and monitor it until
106           termination) and return its status (i.e. $?) in scalar context or
107           the whole process structure in list context; supported options: the
108           ones of proc_create()
109
110       proc_detach([OPTIONS])
111           detach the current process so that it becomes a daemon running in
112           the background (this implies forking and re-opening std*);
113           supported options:
114
115           ·   "callback": code reference that will be executed by the parent
116               process just before exiting and will be given the child pid
117

PROCESS STRUCTURE

119       The process structure (hash) used in this module has the following
120       fields:
121
122       ·   "command": the command being executed, as an array reference
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124       ·   "pid": the process id
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126       ·   "start": the start time, in fractional seconds
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128       ·   "stop": the stop time, in fractional seconds
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130       ·   "status": the status (i.e. $?)
131
132       ·   "timeout": true if the process has been killed because of timeout
133

FILE DESCRIPTOR REDIRECTION

135       When using the "stdin" option of proc_create(), the value can be:
136
137       ·   a string: input will be read from the given file name
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139       ·   a scalar reference: input will be the scalar itself
140
141       When using the "stdout" and "stderr" options of proc_create(), the
142       value can be:
143
144       ·   a string: output will be written to the given file name
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146       ·   a scalar reference: output will be stored in the scalar
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148       ·   a code reference: each time new output is available, the code will
149           be called with two parameters: the process structure and the new
150           output
151
152       In addition, "stderr" can also be given an empty string that means that
153       stderr should be merged with stdout.
154

KILL SPECIFICATION

156       Both proc_create() and proc_terminate() can be given a "kill" option
157       that specifies how the process should be killed.
158
159       The specification is a string containing a space separated list of
160       signal/grace couples, meaning: send the given signal and wait a bit for
161       the process to finish.
162
163       If not specified, the default is "TERM/1 INT/1 QUIT/1", meaning:
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165       ·   send SIGTERM and wait up to 1 second for the process to finish
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167       ·   if the process is still alive, send SIGINT and wait up to 1 second
168
169       ·   if the process is still alive, send SIGQUIT and wait up to 1 second
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171       ·   if the process is still alive, send SIGKILL (implicit)
172

GLOBAL VARIABLES

174       This module uses the following global variables (none of them being
175       exported):
176
177       $Transient
178           true if the process is about to exec() or exit(), there is usually
179           no need to perform any cleanup (e.g. in an END block) for this kind
180           of process
181

AUTHOR

186       Lionel Cons <http://cern.ch/lionel.cons>
187
188       Copyright (C) CERN 2012-2017
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192perl v5.28.1                      2017-08-01              No::Worries::Proc(3)