Additional UNIX Commands

1. Additional UNIX Commands

2. Lecture Overview • Multiple commands and job control • More useful UNIX utilities

3. 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 )

4. 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 15692 Dec 3 23:12 passwd pwd /home/demo echo $p p: Undefined variable.

5. 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

6. 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

7. 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

8. 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 )

9. 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 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" '{}' \;