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Revision as of 12:16, 10 April 2009

Bash Handling

Job Control

Interactive

Key Combinations

Ctrl - r

Ctrl - r allows you to recall-by-typing from the bash history.

Ctrl - o

Ctrl - o alone does nothing, but while pressed when on the line of a with Ctrl - r recalled history entry, it will execute the bash history entry and when it exists, put the next command in history into the shell buffer.

Example:

philip@dinky:~$ vi test.c
philip@dinky:~$ make test
cc     test.c   -o test
philip@dinky:~$ ./test
Hello World!
philip@dinky:~$ (press Ctrl-r vi here)
(reverse-i-search)`vi': vi test.c (press enter here)
philip@dinky:~$ vi test.c
philip@dinky:~$ (press Ctrl-r mak here)
(reverse-i-search)`mak': make test (press Ctrl-o here)
philip@dinky:~$ make test
cc     test.c   -o test
philip@dinky:~$ ./test

Bash Programming

Bash is the most common shell form on linux, and most other unix systems.

Just a small reminder. Before you start writing a long bash script, think if you can do this in perl.

Error and Output Redirect

to redirect output and error

 ls -l 1>normal_out 2>error_out

if you want to have both in one file

 ls -l 1>normal_out 2>&1

Questions and Solutions

Below some examples for bash problems that might come up

Arrays in Bash:

 foo[0]=1;
 foo[1]=2;
 foo[2]=3;
 # loop
 for (( i=0; i<${#foo[@]}; i++ ));
 do
     echo ${foo[$i]};
 done;
 # more like a foreach
 for i in ${foo[@]};
 do
     echo $i;
 done;

Variable Variables

 foobar=5;
 bar="foobar";
 echo $foobar;
 echo $bar;
 echo ${!bar};

Variable Variables in Arrays

 foo[0]=1;
 foo[1]=2;
 foo[2]=3;
 foo_tcp[0]="AT";
 foo_upd[0]="AU";
 foo_tcp[1]="BT";
 foo_upd[1]="BU";
 foo_tcp[2]="CT";
 foo_upd[2]="CU";
 # loop
 for (( i=0; i<${#foo[@]}; i++ ));
 do
     echo ${foo[$i]};
     for k in upd tcp;
     do
         data=foo_${k}[$i];
         echo ${!data};
     done;
 done;

More Documentation

The best advanced guide for bash scripting: http://www.tldp.org/LDP/abs/html/