Additional UNIX Commands

222 Lecture Overview  Multiple commands and job control  More useful UNIX utilities

333 Executing Multiple Commands  Several commands can be executed in a single line, by separating them with ' ; 's:  To run a set of commands in a sub-shell, enclose them within brackets: set a = /home ; echo $a/demo /home/demo ( set a = /home ; echo $a/demo )

444 Executing Commands in a Sub-shell – Example pwd /home/demo (set p = /etc; cd $p ; pwd ; ls -l passwd) /etc -rw-r--r-- 1 root root Dec 3 23:12 passwd pwd /home/demo echo $p p: Undefined variable.

555 The sleep Command  The sleep command just does nothing for the given number of seconds:  Can be useful for interactive scripts  We will use it to demonstrate job control sleep number

666 Job Control  A job is any command line that can be executed by the shell  Multiple jobs can be run concurrently  The shell allows you to manage jobs: Place a job in the background Move a job to the foreground Suspend a job Kill a job

777 Running Jobs in the Background  Typing any command, followed by the ' & ' symbol, will cause the job to be run in the background The job number is printed out for reference  When a job is running in the background, you may continue to type new commands  A message is displayed when the job is complete

888 Running Multiple Jobs  The jobs command will list all current job sleep 10 & [1] 3215 (sleep 5 ; pwd ; sleep 5) & [2] 3216 jobs [1] + Running sleep 10 [2] - Running ( sleep 5; pwd; sleep 5 )

999 Running Multiple Jobs  After 5 seconds, the following is printed:  After a few more seconds:  And finally: /home/demo [1] Done sleep 10 [2] Done ( sleep 5; pwd; sleep 5 )

10 Suspending or Killing the Foreground Job  Pressing Ctrl-Z while some job is running in the foreground will stop its execution The job stops, but is not dead The suspended job will show up in the jobs output, with a status of suspended  Pressing Ctrl-C will completely terminate (or 'kill') the foreground job  The kill command will kill a specific job

11 Moving Jobs Between Background and Foreground  The bg command starts running the specified job in the background The job number should be preceded by a ' % '  The fg command is used to move any background job to the foreground The job will start to run in the foreground, whether it was running or suspended

12 Jobs – Example  We type the following two commands, and press Ctrl-Z immediately after each one: sleep 10 Suspended (sleep 5 ; pwd ; sleep 5) Suspended jobs [1] + Suspended sleep 10 [2] - Suspended ( sleep 5; pwd; sleep 5 )

13 Jobs – Example  Now, we start running the second job in the background:  To move the first job to the foreground: bg %2 [2] ( sleep 5; pwd; sleep 5 ) & /home/demo fg %1 Sleep 10

14 Lecture Overview  Multiple commands and job control  More useful UNIX utilities

15 More Useful Utilities  The UNIX operating system has many other commands  We will briefly review several additional ones now, but you are encouraged to investigate and learn: More commands Additional options and uses for the commands that we have learned

16 Simple Loop – repeat  The repeat command executes any command multiple times  For example: repeat count command repeat 3 echo Hello Hello

17 Date and Time – date  The date command can be used to print the current date and time:  The format argument can be used to control the display of the current time  It may contain literal characters, or special sequences starting with ' % ' date [options] [+format]

18 date – Examples  For example, ' %A ' is the weekday, ' %Y ' is the current year, etc. date +%D 12/04/05 date +"%A, %B %d" Sunday, December 04 date +"Date: %A, %B %d, %Y; Time: %l:%M" Date: Sunday, December 04, 2005; Time: 4:26

19 Getting User Information  Several UNIX commands allow us to get information about other users currently logged-on to the system: who – Shows who is logged on w – Shows who is logged on, and also what they are doing finger – Provides various information about users currently logged-on

20 Splitting Data Streams  The tee command takes input from the standard input, and writes it both to the standard output, and to a list of files:  The following will list all files in the current directory into the file ' all.txt ', and also print a count of all '.c ' files in the directory tee [options] files ls | tee all.txt | grep '.c' | wc -l

21 The find command  The find command searches for files whose name matches a pattern  The most common use of find : Finds all files that match pattern in directory or in any of its sub-directories  find has many other options and uses find directory -name pattern

22 find – Example  find can execute any command  One common use is to execute the grep command on all files:  This will traverse the current directory and all of its sub-directories, and search for the string ' Hello ' in each simple file find. -type f -exec grep -H "Hello" '{}' \;