sort - Sort lines of text files
Summary :
Sort the file contents based on options given to it.
By default the output is showed in the console.
Examples :
$ sort -- Take the input from stdin, sort and output in stdout.
$ sort myfile -o myoutput -- Sort the myfile content and store in "myoutput"
$ sort -b myfile -- Ignore the leading blanks and sort.
$ sort -br myfile -- Same as above but in reverse order
$ sort -c myfile -- Only Check whether myfile is already sorted
$ sort -f myfile -- Ignore the case and sort (a == A)
$ sort -u myfile -- Sort and output only unique lines
$ sort -t : -k 2,2n -k 5.3,5.4 myfile -- Sort numerically on the 2nd field and resolve ties by sorting alphabetically on the 3rd and 4th characters of field 5. Use `:' as the field delimiter
Read : man sort
ulimit - Control the resources available to processes
Summary :
ulimit, Bash Built-in Command, provides control over the
resources (Virtual Mem, Max no .of process, Core file
size, ...) available to processes started by the shell.
If Max no. of user process is set to 5, then the particular
user can't run more then 5 process.
Examples :
$ ulimit -a -- Show All current limits.
$ ulimit -c -- Show core file size (If Core file size is 0, Core file will not be created during the SEG fault).
$ ulimit -c 1000 -- Set new core file size.
$ ulimit -u 3 -- Set max no .of user processes
$ ulimit -n -- Show max open files.
Read : info bash (or) help ulimit
nl - Number lines of files
Summary :
Write each FILE to stdout, with line numbers added.
With No FILE or -, read stdin
Examples :
nl myfile -- Writes all non-empty lines with number.
nl -ba myfile -- Number all lines.
nl -ba -l2 myfile -- Count 2 empty line as 1 and display
nl -nln myfile -- Numbers are left justified.
nl -nrz myfile -- Numbers are right justified and leading zeros
nl -w2 myfile -- Uses 2 column for the line number.
nl -s"> " myfile -- Insert "> " in between number and line.
ls | nl -- ls Output with line numbers
Read : man nl
touch - Change File Timestamps
Summary :
Update the access and modification times of each FILE to the current time.
Examples :
$ touch myfile -- change the time stamp to current time.
If myfile is not there then touch will create it.
$ touch -c myfile -- Same as above. But If myfile is not there, then it won't create it.
$ touch -r f1 f2 -- Set f1's time to f2 instead of current time
$ touch -a myfile -- Change only access time.
$ touch -m myfile -- change only the modification time
$ touch -t 200412251122.33 -- set this time instead of current time
$ ls -lu myfile -- Shows the last access time
Read : man touch
comm - Compare 2 Sorted files line by line
Summary :
Compare two sorted files F1 and F2 line by line.
Examples :
$ comm F1 F2 -- Output contain 3 col.
Col 1 - Uniq to F1, Col 2 - Uniq to F2 and Col 3 - Comman to F1 & F2
$ comm -1 F1 F2 -- Suppress lines unique to F1
$ comm -2 F1 F2 -- Suppress lines unique to F2
$ comm -3 F1 F2 -- Suppress comman lines to F1 & F2
$ comm -13 F1 F2 -- Show lines from F2, which is not in F1
$ comm -23 F1 F2 -- Show lines from F1, which is not in F2
Read : man comm
ls -- List directory contents
Summary :
List the current directory contents and informations.
Examples :
$ ls -- Alphabetically list all files and dir
$ ls -r -- Reverse order
$ ls --color=always -- Output in color
$ ls -F -- Files are classified with /@|= symbols
$ ls -1 -- Output in single column
$ ls -a -- Display hidden entries starting with .
$ ls -R -- Recursive output
$ ls -Q -- Enclose entry names in double quotes
Read : man ls
uname - Display system informations
Summary:-
Display system infos like OS Type, Kernel version, Arch,
Host name etc... Main this uname will collect the info
from the /proc/sys/kernel/{ostype, hostname, osrelease,
version, domainname}.
Examples :-
$ uname -- Kernel Name
$ uname -n -- Show the machine name
$ uname -rv -- Show kernel's release & Ver info
$ uname -om -- Show Arch and OS Type
$ uname -a -- Show all info
Read: man uname
df -- Disk Free and Usage report
Summary:-
df command display the amount of disk space available on
the FileSystem (FS) containing each file name argument.
If no file name is given, the space available on all
currently mounted FSs is shown.
Examples :-
$ df -- Usage report of all mounted FS.
$ df myfile -- Display usage report of FS which contain
the myfile.
$ df /home -- Usage report of Home partition
$ df /dev/hda1 -- Usage report of /dev/hda1
$ df -Th -- Display the partition type and size is in human
readable format
$ df -x tmpfs -- Don't list the 'tmpfs' partitions.
$ df -P -- Output in POSIX format. (Remove -P and see the
difference)
Read: man df
free -- Display Information about Memory utilization
Summary:-
Displays the total amount of free and used physical memory
& swap space in the system, as well as the buffers & cache
consumed by the kernel.
Examples :-
$ free -- Display the mem info in KB.
$ free -m -- Display the mem info in MB.
$ free -m -t -- Display the total mem info.
$ free -s 2 -- Display the mem info for every 2Sec.
$ free -s 2 -c 5 -- Display the mem info for every 2Sec
But only 5 times
$ cat /proc/meminfo -- This is the original info which
is used by free command for the report.
Read: man free
watch - Periodically run and show the output of a program
Summary:
Watch runs command repeatedly, displaying its output This allows you to monitor the program output change over time.
Examples :-
$ watch ls -- Every 2sec(default time) 'ls' is executed and output is showed on the screen.
$ watch -n 6 who -- Every 6Sec 'who' run and list the current users
$ watch -d date -- Highlight the difference b/w successive updates
Press Ctrl+C to stop the Watch Command.
Read: man watch
