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Technical Foundation of Computer Science 5
Network Programming I
Maria Sawaby
Department of Communication and Operating System
April 14, 2015
Net-Dep (Network) Net-Prog I April 14, 2015 1 / 28
Contents
1 Monitoring Programs
2 killing processes
3 Mounting Disk Space
4 Working with Data Files
5 Searching for data
6 Compressing data
bzip2 utility
gzip utility
zip utility
tar utility
7 Summary
Net-Dep (Network) Net-Prog I April 14, 2015 2 / 28
Monitoring ProgramsPeeking at the processes
When a program runs on the system, it's referred to as a process
ps command is used to work with processes
it only shows the processes running on the current terminal
to see everything running on the system:
$ ps -ef
Net-Dep (Network) Net-Prog I April 14, 2015 3 / 28
Monitoring ProgramsPeeking at the processes
This example uses two parameters, the -e parameter, which shows allof the processes running on the system, and the -f parameter, whichexpands the output to show a few useful columns of information
I UID: The user responsible for launching the processI PID: The process ID of the processI PPID: The PID of the parent process (if a process is started by
another process)I C: Processor utilization over the lifetime of the processI STIME: The system time when the process startedI TTY: The terminal device from which the process was launchedI TIME: The cumulative CPU time required to run the processI CMD: The name of the program that was started
The -H parameter organizes the processes in a hierarchical format
try: $ps -efH
Net-Dep (Network) Net-Prog I April 14, 2015 5 / 28
Monitoring ProgramsReal-time process monitoring
The top command displays process information similarly to the ps
command, but it does it in real-time mode
Net-Dep (Network) Net-Prog I April 14, 2015 6 / 28
Monitoring ProgramsReal-time process monitoring
The top command shows the following information:
PID: The process ID of the process
USER: The user name of the owner of the process
PR: The priority of the process
NI: The nice value of the process
VIRT: The total amount of virtual memory used by the process
RES: The amount of physical memory the process is using
SHR: The amount of memory the process is sharing with other
processes
S: The process status (D = interruptible sleep, R = running, S =
sleeping, T = traced or stopped, or Z = zombie)
%CPU: The share of CPU time that the process is using
%MEM: The share of available physical memory the process is using
TIME+: The total CPU time the process has used since starting
COMMAND: The command line name of the process (program
started)Net-Dep (Network) Net-Prog I April 14, 2015 7 / 28
killing processes
The kill command allows you to send signals to processes based on
their process ID (PID)
To send a process signal, you must either be the owner of the process
or be logged in as the root user
e.g the process ID of Firefox is 10959, the command below kills the
process and closes the Firefox
kill 10959
The killall command can be used to end processes based on their
names rather than PID
Net-Dep (Network) Net-Prog I April 14, 2015 8 / 28
Killing processes
Caution!
Be extremely careful using the killall command when logged in as the root
user. It's possible to stop important system processes. This could lead to a
damaged �lesystem
Net-Dep (Network) Net-Prog I April 14, 2015 9 / 28
Mounting Disk SpaceMounting Media
Before you can use a new media disk on your system, you need to
mount it
the command used to mount media is called mount
By default, the mount command displays a list of media devices
currently mounted on the system
There are four pieces of information the mount command provides:1 The device location of the media2 The mount point in the virtual directory where the media is mounted3 The �lesystem type4 The access status of the mounted media
e.g.
$ mount/dev/sda8 on / type ext4 (rw)
Net-Dep (Network) Net-Prog I April 14, 2015 10 / 28
Mounting Disk SpaceMounting Media
The basic command for manually mounting a media device is:
mount -t type device directory
# mount -t vfat /dev/sdb1 /media/maria/new/
# umount /media/maria/new
Net-Dep (Network) Net-Prog I April 14, 2015 11 / 28
Mounting Disk SpaceMounting Media
to mount a .iso image to a location inside your system without havingto burn it to a CD:
I use -o parameter which lets you use other options like "loop" to mountan .iso �le
# mount -t iso9660 -o loop .iso-image dir
Net-Dep (Network) Net-Prog I April 14, 2015 12 / 28
Mounting Disk SpaceThe df Command
Sometimes you need to see how much disk space is available on an
individual device
$ df
using it with -h will show the disk space with human readable form
Net-Dep (Network) Net-Prog I April 14, 2015 13 / 28
The du command
The du command shows the disk usage for a speci�c directory (by
default, the current directory)
you can use the following other options and many more:I -h Print sizes in human-readable formI -m print bloc sizes of 1MI -l count sizes many times if hard linkedI �si Like -h Use power of 1000 instead of 1024
Net-Dep (Network) Net-Prog I April 14, 2015 14 / 28
Working with Data FilesSorting Data
The Linux system provides several command line tools to help us
manage large amounts of data
The sort command does what it says - it sorts data
Net-Dep (Network) Net-Prog I April 14, 2015 15 / 28
Working with Data FilesSorting Data
The -n option is used with sort command to sorting numbers based
on numerical values
$ sort -n �le2
-M is used for month sort $ sort -M �le3
The -n parameter is great for sorting numerical outputs, such as the
output of the du command: $ du -sh * | sort -nr
Net-Dep (Network) Net-Prog I April 14, 2015 16 / 28
Searching for data
Often in a large �le you have to look for a speci�c line of data
somewhere in the middle of the �le, grep command does it easily
format of the command:
grep [options] pattern [�le]
-n option is used to show line number
Net-Dep (Network) Net-Prog I April 14, 2015 17 / 28
Searching for data
-e option is used to �nd more than one patter
If you just need to see a count of how many lines contain the
matching pattern, use the -c parameter
$ grep [tf] �le2 will work like using -e option
Net-Dep (Network) Net-Prog I April 14, 2015 18 / 28
Compressing Data
The zip utility allows you to easily compress large �les (both text and
executable) into smaller �les that take up less space
Linux contains several �le compression utilities:I The bzip2 utilityI The gzip utilityI The zip utilityI Archiving data (tar) its the standard utility used in the linux world
Net-Dep (Network) Net-Prog I April 14, 2015 19 / 28
bzip2 utility
The bzip2 utility is a relatively new compression package that is
gaining popularity, especially when compressing large binary �les
The utilities in the bzip2 package are:I bzip2 for compressing �lesI bzcat for displaying the contents of compressed text �lesI bunzip2 for uncompressing compressed .bz2 �les
Net-Dep (Network) Net-Prog I April 14, 2015 20 / 28
gzip utility
By far the most popular �le compression utility in Linux is the gzip
utility
This package includes the �les:I gzip for compressing �lesI zcat for displaying the contents of compressed text �lesI gunzip for uncompressing �les
Net-Dep (Network) Net-Prog I April 14, 2015 22 / 28
zip utility
The power of the zip utility is its ability to compress entire directories
of �les into a single compressed �le
This makes it ideal for archiving entire directory structures
Net-Dep (Network) Net-Prog I April 14, 2015 24 / 28
tar utility
The format of the tar command is:
tar function [options] object1 object2 ...
This creates an archive �le called test.tar containing the contents of
both the test directory and the test2 directory
tar -cvf test.tar test/ test2/
This lists (but doesn't extract) the contents of the tar �le: test.tar
tar -tf test.tar
This extracts the contents of the tar �le test.tar
tar -xvf test.tar
TIP
If you download open source software, often you'll see �lenames that end in
.tgz. These are gzipped tar �les, and can be extracted using the command
tar -zxvf �lename.tgz.Net-Dep (Network) Net-Prog I April 14, 2015 25 / 28
Summary
The ps and top commands are vital in determining the status of the
system, allowing you to see what applications are running and how
many resources they are consuming
The mount command allows you to mount a physical storage device
into the Linux virtual directory structure. To remove the device, use
the umount command.
The sort utility easily sorts large data �les to help you organize data
the grep utility allows you to quickly scan through large data �les
looking for speci�c information
The Linux tar utility is a popular way to archive directory structures
into a single �le that can easily be ported to another system
Net-Dep (Network) Net-Prog I April 14, 2015 27 / 28