Thursday, August 14, 2008

Linux Commands - Part 5

du - This used to estimate file space usage.

du /home 
{shows usage of /home folder and all other files/folders in home folder}

du -h
/home {show usage in human readable foarmat. Using Mb and Gb}

du –maxdepth=0 /home
{show enrite /home folder usage only, sumerized one}

du –maxdepth=1 /home 
{show enrite /home folder and one level down}

cut - This used to remove sections in each line. This is most of the time used with pipe command

cat /etc/passwd | cut -d":"  -f1
cat /etc/passwd is to show content of the passwd file. We pipe output of that command cut using | (pipe). cut -d":" -f1 {this means split each line of out put by ':' and only display first field (f1)}. Thus if we take only first field we get username. Therefore above command list all the users in our system. 

cat /etc/passwd | cut -d":" -f1-3
{show 1,2,3 field ,example :melick:x:1000}

cat /etc/passwd | cut -d":"  -f1,3
{show 1 and 3 fields ,example :melick:1000}

cat /etc/passwd | cut -c1
{show only first character of each line example :m}

cat /etc/passwd | cut -c1-3
{show 1,2,3 characters of each line example :mel}

cat /etc/passwd | cut -c1,5
{show 1 and 5 characters of each line example :mc}

tr - This command used to translate texts. This is also used with pipe command.

head 5 /etc/passwd | tr '[:upper:]' '[:lower:]'
head 5 /etc/passwd | tr A-Z a-z

head 5 /etc/passwd command will diplay first 5 lines of the passwd file. And we pipe the out put to tr command. And it will translate all text to lower case.

ifconfig - This used to configure a network interfaces. Our network card interface named as eth (Ethernet). Therefore first Ethernet interface is named as eth0. If we have two or more network cards then we have eth1,eth2 as so.. 

ifconfig     {shows only running (up) interfaces details}
ifconfig -a    {show all interfaces details even if down }
ifconfig eth0 192.248.16.100 netmask 255.255.240.0
{this command will add 192.248.16.100 ip address and 255.255240.0 subnet to the eth0 interface}
ifconfig eth0 up           {this will up the interface eth0}
ifconfig eth0 down {this will down the interface eth0}
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