parallel.docbook

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   2
   3 <!--
   4
   5 Written by Joey Hess
   6
   7 -->
   8
   9 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.4//EN"
  10 "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd"
  11 []>
  12
  13 <refentry>
  14         <refentryinfo>
  15                 <address>
  16                         <email>id@joeyh.name</email>
  17                 </address>
  18                 <author>
  19                         <firstname>Joey</firstname>
  20                         <surname>Hess</surname>
  21                 </author>
  22                 <date>2009-07-02</date>
  23         </refentryinfo>
  24
  25         <refmeta>
  26                 <refentrytitle>parallel</refentrytitle>
  27                 <manvolnum>1</manvolnum>
  28                 <refmiscinfo class="manual">moreutils</refmiscinfo>
  29                 <refmiscinfo class="source">moreutils</refmiscinfo>
  30         </refmeta>
  31
  32         <refnamediv>
  33                 <refname>parallel</refname>
  34                 <refpurpose>run programs in parallel</refpurpose>
  35         </refnamediv>
  36
  37         <refsynopsisdiv>
  38                 <cmdsynopsis>
  39                         <command>parallel</command>
  40                         <arg>options</arg>
  41                         <arg>command</arg>
  42                         <command>--</command>
  43                         <arg>argument ...</arg>
  44                 </cmdsynopsis>
  45                 <cmdsynopsis>
  46                         <command>parallel</command>
  47                         <arg>options</arg>
  48                         <command>--</command>
  49                         <arg>command ...</arg>
  50                 </cmdsynopsis>
  51         </refsynopsisdiv>
  52
  53         <refsect1>
  54                 <title>DESCRIPTION</title>
  55
  56                 <para><command>parallel</command> runs the specified command,
  57                 passing it a single one of the specified arguments. This is
  58                 repeated for each argument. Jobs may be run in
  59                 parallel. The default is to run one job per CPU.</para>
  60
  61                 <para>If no command is specified before the --,
  62                 the commands after it are instead run in parallel.</para>
  63
  64         </refsect1>
  65
  66         <refsect1>
  67                 <title>OPTIONS</title>
  68
  69                 <variablelist>
  70
  71                 <varlistentry>
  72                         <term><option>-j maxjobs</option></term>
  73                         <listitem>
  74                                 <para>Use to limit the number of jobs
  75                                 that are run at the same time.</para>
  76                         </listitem>
  77                 </varlistentry>
  78
  79                 <varlistentry>
  80                         <term><option>-l maxload</option></term>
  81                         <listitem>
  82                                 <para>Wait as needed to avoid starting
  83                                 new jobs when the system's load average
  84                                 is not below the specified limit.</para>
  85                         </listitem>
  86                 </varlistentry>
  87
  88                 <varlistentry>
  89                         <term><option>-i</option></term>
  90                         <listitem>
  91                                 <para>Normally the command is passed the
  92                                 argument at the end of its command line. With
  93                                 this option, any instances of "{}" in
  94                                 the command are replaced with the argument.</para>
  95                         </listitem>
  96                 </varlistentry>
  97
  98                 <varlistentry>
  99                         <term><option>-n</option></term>
 100                         <listitem>
 101                                 <para>Number of arguments to pass to a
 102                                 command at a time. Default is 1.
 103                                 Incompatible with -i</para>
 104                         </listitem>
 105                 </varlistentry>
 106
 107                 </variablelist>
 108
 109         </refsect1>
 110
 111         <refsect1>
 112                 <title>EXAMPLE</title>
 113
 114         <para>
 115                 <command>parallel sh -c "echo hi; sleep 2; echo bye" -- 1 2 3</command>
 116         </para>
 117
 118         <para>This runs three subshells that each print a message, delay,
 119                 and print another message. If your system has multiple
 120                 CPUs, parallel will run some of the jobs in parallel,
 121                 which should be clear from the order the messages are
 122                 output.
 123         </para>
 124
 125         <para>
 126                 <command>parallel -j 3 ufraw -o processed -- *.NEF</command>
 127         </para>
 128
 129         <para>This runs three ufraw processes at the same time until
 130         all of the NEF files have been processed.
 131         </para>
 132
 133         <para>
 134                 <command>parallel -j 3 -- ls df "echo hi"</command>
 135         </para>
 136
 137         <para>This runs three independent commands in parallel.</para>
 138
 139         </refsect1>
 140
 141         <refsect1>
 142                 <title>EXIT STATUS</title>
 143
 144
 145         <para>Its exit status is the combination of the exit statuses of each
 146         command ran, ORed together. (Thus, if any one command
 147         exits nonzero, <command>parallel</command> as a whole will exit nonzero.)</para>
 148
 149         </refsect1>
 150
 151         <refsect1>
 152                 <title>NOTES</title>
 153
 154         <para>
 155                 All output to stdout and stderr is serialised through a
 156                 corresponding internal pipe, in order to prevent annoying
 157                 concurrent output behaviour.  Note that serialisation is not
 158                 done on any other file descriptors and file position based
 159                 access to a nonstandard file descriptor might have unexpected
 160                 results.
 161         </para>
 162
 163         </refsect1>
 164
 165         <refsect1>
 166                 <title>AUTHOR</title>
 167                 <para>
 168                         Tollef Fog Heen
 169                 </para>
 170         </refsect1>
 171
 172 </refentry>