xjobs(1) User Commands xjobs(1)NAMExjobs - construct command line and execute jobs in parallel
SYNOPSISxjobs [options] [utility [argument ...]]
DESCRIPTIONxjobs reads job descriptions line by line and executes them in paral‐
lel. It limits the number of parallel executing jobs and starts new
jobs when jobs finish. Therefore, it combines the arguments from every
input line with the utility and arguments given on the command line. If
no utility is given as an argument to xjobs, then the first argument on
every job line will be used as utility. To execute utility xjobs
searches the directories given in the PATH environment variable and
uses the first file found in these directories.
xjobs is most useful on multiprocessor machines when one needs to exe‐
cute several time consuming commands that could possibly be run in par‐
allel. With xjobs this can be achieved easily, and it is possible to
limit the load of the machine to a useful value. It works similar to
xargs, but starts several processes simultaneously and gives only one
line of arguments to each utility call.
By using I/O redirectors the standard input, output, and error stream
of executed jobs can be redirected. Use < to redirect standard input, >
to redirect standard output, >! to redirect standard output and over‐
write an existing file, >> to append standard output to an existing
file, >& to redirect both standard output and standard error output to
the same file, and >>& to append both standard output and standard
error output to the same file.
If passed on the command line, these operators specify the default I/O
redirection that can be overwritten by specifying another redirector to
a specific job on its argument line. After all these operators a file‐
name is expected. See EXAMPLES below for an example. If you need more
advanced shell features than the redirection operators supported by
xjobs, then use as utility a shell of your preference.
Every job line can be preceeded by a "cd directory;" command that tells
xjobs in which directory the job shall be executed. For every line this
can only be used once. For more complex scripting, please pass the line
to execute to a shell of your choice.
xjobs constructs the arguments of the jobs to execute from each input
line. Each input line will create a seperate job, whereas newline char‐
acter are handled as regular whitespace by xargs. To be able to include
whitespace charakters in arguments, either preceed them with a back‐
slash or quote them with single or doublequote charakters. A backslash
charakter preceeding a newline will make xjobs ignore the newline char‐
acter, thus giving you the ability to pass arguments for a single job
across multiple lines. To include quotation marks in quoted arguments,
preceed them with a backslash. Lines passed to xjobs beginning with a
# charakter are interpreted as comments.
Finally, xjobs also includes a mechanism for serializing the execution.
Like this it is possible to parallelize independent jobs and sequence
jobs that have a dependency. This can be achieved by inserting a line
that only consists of two percentage charakters in sequence (%%). All
jobs before this sequence point are executed at the requested number of
jobs in parallel. When hitting the sequence point xjobs waits for all
processes to finish and then continues starting jobs that follow the
sequence point.
When passing a named pipe (i.e. a file name created by mkfifo) via
option -s as an input, xjobs will close and reopen the fifo when reach‐
ing end-of-file. Like this it is possible to setup an xjobs server and
sending jobs to this server from muliple programs. See section EXAMPLES
below for an example.
OPTIONS-j <jobs>
Sets the maximum number of jobs that are started in parallel.
The default value is to limit the number executing jobs is equal
to the number of online processors in the system. If the number
passed as <jobs> is followed by an 'x' charakter (e.g. 2.5x),
the value is multiplied with the number of online processors
before setting the job limit. I.e. having a machine with 4
online processors and passing 2.5x as an argument to option -j
will yield a joblimit of 10 jobs.
-s <script>
Use file script instead of the standard input to read the job
descriptions.
-n Redirect standard output and standard error output of executed
jobs to /dev/null.
-l <num>
Combine the arguments of <num> input lines for a single job.
-p Start jobs interactively, prompting the user.
-q <num>
Limits the number of queued jobs to num elements. Normally xjobs
reads in jobs from standard input or the give script and queues
them if they cannot be started at once. With this option, xjobs
will stop reading as soon as num jobs are queued and restart
reading when a new job has been started. Like this xjobs allo‐
cates less memory. Use this option, if you pass huge number of
jobs to xjobs, to limit memory consumption. It can also increase
performance of xjobs, but be sure that jobs get fed fast enough
to xjobs.
-1 Pass one argument per job, which is expected to be terminated by
a new-line character. No argument parsing is performed. That way
it is more easy to process jobs where arguments may include
whitespace character or other tokens that influence argument
parsing.
-0 Same as -1, but as a job and argument termination character a
null-character (\0) is expected instead of a new-line character.
That way also arguments with new-line character can be processed
without escape sequences.
-V Print the version number of xjobs and exit.
-v <level>
Set verbosity of xjobs to level. Valid leves are: 0=silent,
1=error, 2=warning, 3=info, 4=debug. The default level of ver‐
bosity is 3.
EXAMPLES
If you have a lot of .zip files that you want to extract, then use
xjobs like this:
$ ls -1 *.zip | xjobs unzip
If you want to do the same without getting the output of each unzip
task on your terminal, then try this:
$ ls -1 *.zip | xjobs-n unzip
To gzip all *.bak files in a given directory hierarchy, use it the fol‐
lowing way:
$ find . -name '*.bak' | xjobs gzip
To generate index files for a set of *.jar files, you can use the redi‐
rection feature of xjobs, and do the following:
$ ls -1 *.jar | sed 's/\(.*\)/\1 > \1.idx/' | xjobs jar tf
If you also want to capture the error output, than use >& instead of >.
You can also use it to execute several different commands. Therefore,
write a script file that contains every job you want to execute and
pass it to xjobs with the option -s:
$ cat - > script
unzip my.zip
tar xf my.tar
lame --silent my.wav my.mp3
crypt notsecret < mydata > secretfile
^D
$ xjobs-s script
To be able to queue up jobs from multiple sources with xjobs, use a
named pipe and pass it explicitly as input script. Then write the jobs
to the named pipe:
$ mkfifo /var/run/my_named_pipe
$ xjobs-s /var/run/my_named_pipe &
$ echo unzip 1.zip >> /var/run/my_named_pipe
$ echo tar cf /backup/myhome.tar /home/me >> /var/run/my_named_pipe
ENVIRONMENT VARIABLES
PATH Determines the location of command.
AUTHORS
Thomas Maier-Komor <thomas@maier-komor.de>
Donations via PayPal are welcome!
HOMEPAGE
http://www.maier-komor.de/xjobs.html
LICENSE
GNU General Public License Version 2
SEE ALSOxargs(1)Thomas Maier-Komor 20100915 xjobs(1)
