#!/bin/sh
echo "###############################"
echo " Hardware Details "
echo "###############################"
echo "HostName:`uname -n`"
echo "Machine Name:`uname`"
echo "Processor Name:`uname -p`"
echo "##############################"
echo " Software details "
echo "##############################"
echo "Os Name:`uname -o`"
echo "Os Release:`uname -r`"
echo "Od version:`uname -v`"
Shell Script to find out if a rectangle type
echo "Enter Angle A:"
read A
echo "Enter Angle B:"
read B
echo "Enter Angle C:"
read C
if [ $A -eq 90 -o $B -eq 90 -o $C -eq 90 ]
then
echo "This is Right angled Triangle"
elif [ $A -gt 90 -o $B -gt 90 -o $C -gt 90 ]
then
echo "This is Obtuse angled Triangle"
elif [ $A -lt 90 -a $B -lt 90 -a $C -lt 90 ]
then
echo "This is acute angled Triangle"
fi
the first line in the shell script should be the interpreter location to be used
#!/bin/bash ----> this interpreter is taken to execute the file
if this is not there the shell which launched this will be taken.
echo –n no new line
eco –e take special
| Double Quotes | does interpolation , substitutes with var value |
| Single Quotes | no manipulation directly prints |
| Back Quotes | executes a command and gives us output. |
Special variables in shell
program to print
echo "program name is $0"
echo "argument one dollar 1 $1"
echo "argument two dollar two $2"
echo "argument three Dollar three $3"
IFS=":"
echo "all args $@ "
echo "all args with delimiter $* "
If in Shell Script:
if test $x –lt $y
OR
if [$x –lt $y]
Check the file properties
root@v11> if [ -e shell.sh ]; then echo yes ; else echo no; fi
yes
root@v11> if [ -f shell.sh ]; then echo yes ; else echo no; fi
yes
root@v11> if [ -d shell.sh ]; then echo yes ; else echo no; fi
no
root@v11> if [ -L shell.sh ]; then echo yes ; else echo no; fi
no
root@v11> if [ -r shell.sh ]; then echo yes ; else echo no; fi
yes
Case in Shell Script:
case $1 in
a) echo "this is a";;
b) echo "this is b";;
c) echo "this is c";;
*) echo "this is default";;
esac
While in Shell Script:
num=0;
while [ $num -lt $# ]
do
echo $num
num=$[num+1]
done
Until in Shell Script:
For in Shell Script:to print all the command line arguments passed using for
for i in $@
do
echo $i
done
Handling Signals
trap "echo trapped; exit;" SIGINT
while [ 1 ]
do
echo "hi"
done
SET
shows the list of environment variables
[trainee@localhost purna]$ set
BASH=/bin/bash
BASH_ARGC=()
BASH_ARGV=()
BASH_LINENO=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="3" [1]="1" [2]="17" [3]="1" [4]="release" [5]="i686-redhat-linux-gnu")
BASH_VERSION='3.1.17(1)-release'
COLORS=/etc/DIR_COLORS.xterm
COLUMNS=80
tar
to tar
tar –cvf <file.tar> input files list
untar
tar –xvf <file.tar>
tar –zxvf will unzip and untar it.
crontab:
l list
e edit
r remove
format of the file
| minutes | hour | day | month | days of week | Command |
0 * * * “mon-sat” echo “Hello”
every hour you get a hello message.
the output of the above is sent to mail.
Program ?
INIT: Mother of all the processes.
Rights of Process
Orphan Process :
the process whose parent died,when a parent process is killed the INIT process takes the responsibility that's the reason its called mother of all the processes.
Zombie Process :
A process
PS
processes running on your terminal
[trainee@localhost purna]$ ps
PID TTY TIME CMD
6188 pts/14 00:00:00 bash
6507 pts/14 00:00:00 ps
number of processes running
[trainee@localhost purna]$ ps -e|wc -l
164
processes running on a terminal pts/3
[trainee@localhost purna]$ ps -tpts/3
PID TTY TIME CMD
4300 pts/3 00:00:00 bash
6612 pts/3 00:00:00 cat
DAEMON
Disk And Execution Monitor
JOBS
will print all the jobs which are stopped or paused .
to resume these jobs one can use fg or bg (foreground or background) %JOB_NUMBER
KILL
list all signals
[trainee@localhost purna]$ kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL
5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE
9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2
13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT
17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU
25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH
29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN
35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+338)SIGRTMIN+4}Dummy signals
39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12
47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14
51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10
55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6
59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX
Kill A Process
[trainee@localhost purna]$ kill -s SIGKILL 4524
where 4524 is the process id
Nice
the lesser the Nice value the higher the priority
only the root can make the priority higher or nice value to low.
Regular Expression:
| [.] DOT | dot matches for a single character |
| [abcd] | matches one of the list ,say [abcd] matches one of a,b,c,d |
| [a-d] | matches the range of characters a to d |
| [^a-i] | should not contain the range a to i |
| [a*] ~= {0,} | match zero or more a’s |
| [a+] ~= {1,} | match one or more a’s |
| [a?] ~= {0,1} | zero or one occurance of letter a |
| wh(at|en|ere} | what when where , you can specify group of letters and also a pipe to mark OR operator |
| ^not | start with string not,notify,notice etc…… |
| not$ | end with not like knot |
GREP: search Globally for Regular Expression and Print
| grep | option[s] |
| -n number in the file | |
| -c count the number of occurrences, unlike wc –l it gives the file wise count | |
| -A context selection After -B Context selection Before you can specify number with A or B | |
| -l List the names of files | |
| -r recursively Grep | |
| -s , if there are permission errors it suppresses | |
| -e used to search multiple regular expressions |
Egrep: Extended GREP { More operators +,?,(),|}
Fgrep: Fixed length Grep , does not support operators
VI – Visual Editor.
| Normal | no sign |
| Command Line | : colon |
| Input | INSERT/REPLACE |
Normal –> Insert mode a,i,o,r,s A,I,O,R,S
Esc/Enter –> to normal mode.
: to command line mode.
H
-{minus} k
0<----h * l---->$ ----------------------->M
Enter j
L
GG= go to line number
x delete command
X replacement for back space
u undo char by char
U undo at once
DW delete a word
DD delete a whole line
repeat a command 5x will delete 5 chars meaning number specifies number of times the command has to be executed.
| q | quit, vi wont allow if there are any changes done. |
| q! | quit without saving |
| wq | write and quit |
| wq <filename> | save as file name and quit,if file not exists |
| wq! <filename> | save as file name and quit,if file exists |
| r! <Command> | run the command and put the output at the cursor position |
| sh | takes u to shell from vi ,where you can execute commands and come back. |
file: give the type of the file , which is determined using the extension of the file.
[trainee@localhost purna]$ file *
as: directory
f2: empty
f3: ASCII text
f4: ASCII text
f5: ASCII text
WC: gives the word count in a file or some stream of data.
c=character count
l = line count
L = length of the longest line
w= word count
split: split a file into many parts , the default is 1000 lines but you can use –l option and specify number of lines.
[trainee@localhost purna]$ split -l 5 f5
[trainee@localhost purna]$ ls
as f3 f5 g1 xaa xac xae xag xai
f2 f4 fruits g2 xab xad xaf xah xaj
splits f5 file to many files like
xaa xac xae xag xai
xab xad xaf xah xaj
cmp: check if two files are same
when they are equal there is no output
else it looks like this
[trainee@localhost purna]$ cmp xaa xab
xaa xab differ: byte 1, line 1
[trainee@localhost purna]$ cmp -l xaa xab
1 40 61
2 40 70
4 40 61
5 40 71
DISK TYPES
Linux Partition
| Boot block | Super Block | I node table | Data Block |
Boot Block : has information to boot
Super Block: has all summary of the parition
Inode : all properties of files are stored {except this everything else is present in INODE file number,name,data}
Inode table is list of Inodes
Inode looks like this
| Type |
| permissions |
| uid/gid |
| timestamp |
| links Count--->when more than file names which refer to the inode then this is incremented. |
| size |
| Pointer to the disk Block |
Data Block: is the place where actual data is stored.[Data Block Pointers]
| PTR 1 |
| PTR 2 |
| PTR 11 – > pointer to a list of pointers |
| PTR 12 – > double indirection |
Hard Links:
has the same i-node number with different file name
when original file is deleted the link file is still present until the hard link count is 0
ln <target name> <link name>
ln <targets> <dest dir>
hard links are not allowed for directories
Every time a directory is created it has 2 hard links the path and the [.]
and when a sub dir is created the .. becomes another link
Soft Links:
the size of the file is the path length.
when the original file is deleted this symbolic link becomes invalid.
permission of symbolic link is 777 which is of no use.
when user tries to change permission on soft link it might affect the original file.
same as hard link except that you need to give an option –s
soft links are allowed for directories
Check Inode number:
[trainee@localhost purna]$ ls -li
total 1
Inode number---------hardlink count
3702945 drwxrwxr-x 2 trainee trainee 4096 Jun 14 15:03 file1
| Text | Binary | Directory | |
| Read | cat <file> | cp /bin/ls | ls |
| Write | cat > <file> | cc a.c | rm <directory> |
| eXecute | ./<file> | ls | cd <directory> |
Only 2 users can change the permissions of a file
ls -l
Owner-Group-Others HardLinks username groupName bytes date filename
drwxrwxr-x 2 trainee trainee 4096 Jun 14 15:03 as
-rw-rw-r-- 1 trainee trainee 0 Jun 14 14:27 f2
-rw-rw-r-- 1 trainee trainee 148 Jun 14 14:28 f3
-rw-rw-r-- 1 trainee trainee 148 Jun 14 14:28 f4
-rw-rw-r-- 1 trainee trainee 888 Jun 14 14:29 f5
-rw-rw-r-- 1 trainee trainee 0 Jun 14 15:10 fruits
-rw-rw-r-- 1 trainee trainee 0 Jun 14 15:10 g1
-rw-rw-r-- 1 trainee trainee 0 Jun 14 15:10 g2
Change permissions on a file
UMASK:
you can find out umask by typing umask
[trainee@localhost purna]$ umask
0002 the last three specify what permission to deny to the owner group and others
input----> Command ----> Output
input redirection <
output redirection >
cat f1 > f2
to concatenate
to display file contents
copy files
cat without any arguments ….takes from the terminal and writes to the terminal so reads from keyboard and displays on screen this will be infinite loop .
cat f1 >> f2 [APPEND]
Less:
read from standard input and show page by page on standard output.
Touch:
ls- lists the files/directories in a directory
/[Slash]- Root directory
dev: all devices
lib: library's for every one.
lost+found: specific to redhat recovered files
Misc: miscellaneous.
proc: mapping to memory.
tmp : temporary files
var : variety of log files
bin: binaries of commands like ls mkdir etc.
boot: boot loader files, kernel etc
sbin: system binaries
mnt: any mountable devices like cdrom pendrive are mounted under this.
./ : current working directory
.. : parent directory
~ : Home directory (available only in few shells)
PWD : print working directory
CD: change directory, cd without any arguments takes to the home directory
to go to home u can use cd $HOME , cd ~ or just cd.
mkdir: <dir name …..>make a directory, on success does not give any message ,, instead u can use –V for verbose.
mkdir –p make parents as necessary.
rmdir <dir name ….> removes the specific dir
ls *: all the files
ls f?: list files which start with f and have one more leter.
ls f[1234]/ls f[1-4]: f followed by one of 1-4
Note for copy and move
Copy:
cp <source file> <dest file>
cp <source files…….> <dest file>
Move:
mv <source file> <dest file>
mv <source files…….> <dest file>
Delete:
rm: removes files completely very hard to recover.
rm –rf ~ [ most dangerous command ]
root@v11geonode2> cat /etc/passwd
root:x:0:0:Super-User:/root:/sbin/sh
daemon:x:1:1::/:
bin:x:2:2::/usr/bin:
USERNAME : PASSWORD:USERID:GROUPID
the password encrypted is stored at /etc/shadow
vin:$1$3vD2BLH4$ZEFSMbnDYrJ4YGEqzKDR0/:14734:7:91:7:::
user2:$1$19HkQt88$DBFe7VgQpGdd7osh9Oe8m1:14735:7:91:7:::
vin1:$1$0YwoL0i8$/Jg7ZnPs50lxlSax3Nc5C0:14742:7:91:7:::
logout
Shutdown
Shells
| COMMAND | OPTIONS | ARGUEMENTS |
| internal/external | character or string | optional |
Who Am I [aka who –m] : tells who the logged in user is
root@v11geonode2> who am i
root pts/2 Jun 14 12:18 (10.142.208.146)
user terminal Login Time IP-Address
actually who with any two options will return the same
you can actually type who mom likes / who dad likes tooo
WHO : all the users
root@v11geonode2> who
rtp99 pts/1 Jun 14 11:16 (10.142.216.148)
root pts/3 Jun 14 12:20 (10.142.216.164)
root pts/4 Jun 14 12:27 (10.142.216.158)
root pts/7 Jun 14 10:34 (10.142.216.158)
-U gives idle time
id
[trainee@localhost /]$ id
uid=500(trainee) gid=500(trainee) groups=500(trainee) context=user_u:system_r:unconfined_t
[trainee@localhost /]$ id -u
500
[trainee@localhost /]$ id -g
500
[trainee@localhost /]$ id -G
500
[trainee@localhost /]$ id -nu
trainee
[trainee@localhost /]$ id -ng
trainee
[trainee@localhost /]$ id -nG
trainee
about Us
root@v11geonode2> logname
root
root@v11geonode2> tty
/dev/pts/2
Hardware Information
[trainee@localhost /]$ uname -s
Linux
[trainee@localhost /]$ uname -o
GNU/Linux
[trainee@localhost /]$ uname -p
i686
[trainee@localhost /]$ uname -m
i686
[trainee@localhost /]$ uname -n
localhost.localdomain
[trainee@localhost /]$ uname -r
2.6.18-8.el5
[trainee@localhost /]$ uname -v
#1 SMP Fri Jan 26 14:15:21 EST 2007
[trainee@localhost /]$ uname -a
Linux localhost.localdomain 2.6.18-8.el5 #1 SMP Fri Jan 26 14:15:21 EST 2007 i686 i686 i386 GNU/Linux
Date
Mon Jun 14 13:03:43 IST 2010
Changing password
root@v11geonode2> passwd
passwd: Changing password for root
New Password:
root can set some stupid and simple passwords.
Calculator(powerful but not user friendly)
[trainee@localhost /]$ bc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
2+3
5
x=2
y=3
z=x+y
print z
5
quit
Linux has 10k commands so …learn to use the manual[Manual pages]
man [Command]
info
more user friendly help
it has hyper links in the form of *[Star]
--help
only few commands support this , brief explanation
whatis kill
lists the sections
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