10-14-2016
You're welcome,
-a means read into an array (when using
bash).
F is the name of the array
printf is the preferred and standardized alternative to
echo. The first field to
printf is the "format string" . "%s" means "string" and "\n" means new line". See:
printf or the bash man page.
To get all the element of the array one normally uses:
"${F[@]}"
"${F[@]# }" does the same, but in addition it uses
parameter expansion and
# means cut off a leading space if it exists.
Since
F is an array it will work on every element of the array (more about this in the bash man page).
With the while read loop, for every line of the input file, the array
F gets filled anew.
Last edited by Scrutinizer; 10-14-2016 at 05:34 AM..
This User Gave Thanks to Scrutinizer For This Post:
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LEARN ABOUT CENTOS
trace-cmd-extract
TRACE-CMD-EXTRACT(1) TRACE-CMD-EXTRACT(1)
NAME
trace-cmd-extract - extract out the data from the Ftrace Linux tracer.
SYNOPSIS
trace-cmd extract [OPTIONS]
DESCRIPTION
The trace-cmd(1) extract is usually used after trace-cmd-start(1) and trace-cmd-stop(1). It can be used after the Ftrace tracer has been
started manually through the Ftrace pseudo file system.
The extract command creates a trace.dat file that can be used by trace-cmd-report(1) to read from. It reads the kernel internal ring buffer
to produce the trace.dat file.
OPTIONS
-p plugin
Although extract does not start any traces, some of the plugins require just reading the output in ASCII format. These are the latency
tracers, since the latency tracers have a separate internal buffer. The plugin option is therefore only necessary for the wakeup,
wakeup-rt, irqsoff, preemptoff and preemptirqsoff plugins.
With out this option, the extract command will extract from the internal
Ftrace buffers.
-O option
If a latency tracer is being extracted, and the -p option is used, then there are some Ftrace options that can change the format. This
will update those options before extracting. To see the list of options see trace-cmd-list. To enable an option, write its name, to
disable the option append the characters no to it. For example: noprint-parent will disable the print-parent option that prints the
parent function in printing a function event.
-o outputfile
By default, the extract command will create a trace.dat file. This option will change where the file is written to.
SEE ALSO
trace-cmd(1), trace-cmd-record(1), trace-cmd-report(1), trace-cmd-start(1), trace-cmd-stop(1), trace-cmd-reset(1), trace-cmd-split(1),
trace-cmd-list(1), trace-cmd-listen(1)
AUTHOR
Written by Steven Rostedt, <rostedt@goodmis.org[1]>
RESOURCES
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git
COPYING
Copyright (C) 2010 Red Hat, Inc. Free use of this software is granted under the terms of the GNU Public License (GPL).
NOTES
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
06/11/2014 TRACE-CMD-EXTRACT(1)