Command Language

I/O redirection and pipe

% command                 running in foreground (interactive)
% command >file           redirects stdout to file
% command 2>err_file      redirects stderr to err_file
% command >file 2>&1      redirects both stdout and stderr on file
% (command > f1) 2>f2     send stdout on f1, stderr on f2
% command >>file          appends stdout to file
% command <file           redirects stdin from file
% command << text         Read standard input uo to line identical
                          to text
% command1  |  command2   redirects stdout from command1 into stdin
                          of command2 via a pipe
                          Ex :  du ~ | sort -nr | head 
% command | tee f1 f2 ... The output of command is sent on
                          stdout and copied into f1, f2, ...
% command&                running in background
% nohup command&          running in background even after log out
% set -o monitor          to have a message when a background job ends
stderr : to print on it in a script, use the option -u2 in command 
         print

Shell variables

# Warning : no blank before of after the = sign
# Integers :
    n=100  ;  x=&n
    integer t
    typeset -r roues=4 # definition of a CONSTANT (read only)
    typeset -i2 x      # declares x as binary integer
    typeset -i8 y      # declares y as octal integer
    typeset -i16 z     # guess what ?
# Strings  :
    lettre="Q" ; mot="elephant"
    phrase="Hello, word"
    print "n=$n ; lettre=$lettre ; mot=$mot ; phrase=$phrase"
    typeset -r nom="JMB"    # string constant
# Arrays   :  one dimensional arrays of integers or strings
#             automatically dimensionned to 1024
    animal[0]="dog" ; animal[1]="horse" ; animal[3]="donkey"
    set -A flower tulip gardenia " " rose
    print ${animal[*]}
    print ${flower[@]}
    print "cell#1 content : ${flower[1]}

Pattern matching

Tilde Expansion :
    ~                    your home directory (ls ~)
    ~edmund       home directory of another user
    ~+                  absolute pathname of the working directory
    ~-                   previous directory (cd ~-) ( or cd -)

Control characters

< ctrl_c> Cancel the currently running process (foreground)
< ctrl_z> Suspend the currently running process
    then : > bg           : to send it in background
    or     > fg           : continue in foreground
    or     > kill -option : sends signals (such as TERMINATE)
    ex     > kill -9 pid  : to kill a background job
             kill -l      : to find out all the signals 
                            supported by your system.
< ctrl_d> End of file character
$ stty       to see what are the KILL & <EOF> characters