Friday, May 10, 2013

Quick Linux (6): Shell (Overview)

Chapter 5: The Shell
ls -- -l #-- indicates the end of options
PATH = $PATH:. #adds current working directory to the path

s234-155:~ nemo$ who
nemo     console  May 10 17:55 
nemo     ttys000  May 10 21:41 

$ who #The device name that's displayed after your username is the filename of the screen and keyboard

$echo hello > t.txt #If the file exists, the shell will overwrite it

$echo hello >> t.txt #The append output symbol (>>) appends a file 

* The /dev/null device is a data sink, "bit bucket". You can redirect output that you do not want to keep or see to /dev/null

$ who | tee who.out | grep nemo #use tee to redirect output to both a file and standard output

$ jobs 

* To run a job in the background use & at the end of a command or bg

* To bring a job back to the foreground: type fg or % followed by the job number
to get the current running jobs type

* To kill a job $kill PID (process number)

? #generates filenames that have "tes" followed by a single character
$ ls test.tx?

* #matches any number of characters unlike ? 
$ ls te*

[] #match filenames containing the individual characters, use hyphen for range
s234-155:Linux nemo$ ls
another hello.txt linktest test.txt
s234-155:Linux nemo$ echo [hl]*
hello.txt linktest
s234-155:Linux nemo$ echo [a-f]*

special cases: [] with ! and ^
[!a-f]* #means not to include the characters at the beginning 
*[^ab] #don't end with those characters

(to list them $info bash, Shell Builtin Commands)
The shell does not fork a new process when running a builtin. 

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