UNIX Commnads for BASIS

CREATING AND DELETING FILES

cat > filename
file will be created
cat >> filename
append contents to existing file.
touch file1 file2
no.of files will be created.
rm filename
file will be deleted.


CREATING AND REMOVING DIRECTORIES


mkdir dir1 dir2 no.of directories will be created.
rmdir dir1 dir2 no.of empty directories will be deleted
rm –rf dir1 it removes directories with contents.
cd to change one directory to another directory
pwd to know present working directory.
ps –ef to know all processes.
kill pid to kill particular process.
kill –9 pid to kill process forcefully.
vi filename to edit file in vi.




ls filename Lists all files and directories.
ls –l it gives full information of files and directories.
ls –a it displays hidden files
ls –p shows difference b/w files and directories.
ls –i Displys inode no of files and directories.


FILE PERMISSIONS


We have two ways to assign permissions to files
1. Numeric mode
2. Symbolic mode or relative mode


1)Numeric mode

We assign numerics to permissions like
read 4
write 2
execute 1
chmod 777 filename/dirname
assign full permissions to all users.
chmod 666 filename/dirname
it assigns read and write permissions to all users
chgrp newgroupname file/directory
it changes groupname for file or directory.
chown newownername file/directory
it changes owner for file or directory.


2)Symbolic mode or relative mode


Here we assign symbols to users.
owner u
group g
others o
all a
read r
write w
execute x
adding permissions +
removing permissions -


To assign permissions - chmod ugo+rwx file/dir.
To remove permissions - chmod ugo-rwx file/dir.



Network communication
*********************

In hetrogenous and homogenous environment

telnet ipaddress - it connets to remote system
ftp ipaddress
scp /dir ipaddress:/dir
it copies date from source system to target system
ssh ipaddress:mkdir /dir - it executes commands in remote system.



Only in homogenous environment

rlogin ipaddress

rcp /dir ipaddress:/dir

rsh ipaddress:rm /file

User commads

useradd –u uid –g gid –G gid –d homedirecory –m –s sh username
it adds user g for primary group
G for secondary group
d,m for homedirecoty
s for default shell
u user id
su – username to swith from one user to another user.
who displays all users who are currently logged in system.
who am I displays detailed information about current logged in user.
last displays information about when system is lastly
rebooted,who,time.
finger information about current logged in user.



filesystems



df
it displays all filesystems with sizes
df –h
it displays all filesystems with human readable form.

du to know disk utilization




Shutdown commands




shutdown
init 0
like shutdown
init 1
single user mode
init 6
like reboot
reboot
poweroff


copy or move

To copy a file
cp sourcefile targetfile
To copy empty directory
cp sourcedir targetdir
To copy directory with all contents
cp –r sourcedir targetdir
To move file
mv sourcefile targetfile
To move directory
mv sourcdir targetdir



creating links


To link file or directory in same filesystem
ln soucefile/dir targerfile/dir
this is called hard mounting
If you link souce file or dir with another file which is in different file system that is called soft mounting
ln –s sourcefile/dir targetfile/dir
For help
man command




Pattern search


To seach for a single word in a file
grep word filename
it displays all lines which contains this word
To seach multiple words
egrep word1 | word2 filename
To seach for a text
fgrep text filename



find

searches in current directory for file or directory.

find . –name “/” –type f/d -print


type options:

b block (buffered) special

c character (unbuffered) special

d directory

p named pipe (FIFO)

f regular file

l symbolic link

to search files exact n th day old from now


find . –name “/” –mtime n –print


to search files morethan n days old from now.


find . –name “/” –mtime +n –print


to search files from n days old from now.

find . –name “/” –mtime -n –print


for searched files in range( from more than 64 days old to 95 days old)

find . -name "*" -a "(" -mtime +64 -a -mtime -95 ")" -exec ll {} \;



to know files in current directory which are more than 10M size.

find . -type f -size +10M -exec ls -l {} \; (for files)
or

find . -xdev -size +10000000c -exec ls -l {} \; (for files and directories)


`b' for 512-byte blocks (this is the default if no suffix
used)

`c' for bytes

`w' for two-byte words

`k' for Kilobytes (units of 1024 bytes)

`M' for Megabytes (units of 1048576 bytes)

`G' for Gigabytes (units of 1073741824 bytes)



If you want to see if you have any directories with world write permission, use:
find . -type d -perm 777 –print