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Full Discussion: test condition
Top Forums Shell Programming and Scripting test condition Post 302264210 by tostay2003 on Wednesday 3rd of December 2008 11:42:18 AM
Old 12-03-2008
test condition

Hi there,

I tried to search for this almost everywhere, but didnt get any proper information on it.

What is the difference between

Code:
[[  ]]

[ ]

Some of the code works when I have only single condition i.e.

Code:
[[ -z $arg1 ]] && $dothis1 || $dothis2

But if i try to include another testcondition to the above code like below

Code:
[[ -z $arg1 -a -n $arg2 ]] && $dothis1 || $dothis2

This works when I replace with single square brackets
Code:
[ -z $arg1 -a -n $arg2 ] && $dothis1 || $dothis2

Why is that so?
 

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DDB(8)							    BSD System Manager's Manual 						    DDB(8)

NAME
ddb -- configure DDB kernel debugger properties SYNOPSIS
ddb capture [-M -core] [-N -system] print ddb capture [-M -core] [-N -system] status ddb script scriptname ddb script scriptname=script ddb scripts ddb unscript scriptname ddb pathname DESCRIPTION
The ddb utility configures certain aspects of the ddb(4) kernel debugger from user space that are not configured at compile-time or easily via sysctl(8) MIB entries. To ease configuration, commands can be put in a file which is processed using ddb as shown in the last synopsis line. An absolute pathname must be used. The file will be read line by line and applied as arguments to the ddb utility. Whitespace at the beginning of lines will be ignored as will lines where the first non-whitespace character is '#'. OUTPUT CAPTURE
The ddb utility can be used to extract the contents of the ddb(4) output capture buffer of the current live kernel, or from the crash dump of a kernel on disk. The following debugger commands are available from the command line: capture [-M core] [-N system] print Print the current contents of the ddb(4) output capture buffer. capture [-M core] [-N system] status Print the current status of the ddb(4) output capture buffer. SCRIPTING
The ddb utility can be used to configure aspects of ddb(4) scripting from user space; scripting support is described in more detail in ddb(4). Each of the debugger commands is available from the command line: script scriptname Print the script named scriptname. script scriptname=script Define a script named scriptname. As many scripts contain characters interpreted in special ways by the shell, it is advisable to enclose script in quotes. scripts List currently defined scripts. unscript scriptname Delete the script named scriptname. EXIT STATUS
The ddb utility exits 0 on success, and >0 if an error occurs. EXAMPLES
The following example defines a script that will execute when the kernel debugger is entered as a result of a break signal: ddb script kdb.enter.break="show pcpu; bt" The following example will delete the script: ddb unscript kdb.enter.break For further examples, see the ddb(4) and textdump(4) manual pages. SEE ALSO
ddb(4), textdump(4), sysctl(8) HISTORY
The ddb utility first appeared in FreeBSD 7.1. AUTHORS
Robert N M Watson BUGS
Ideally, ddb would not exist, as all pertinent aspects of ddb(4) could be configured directly via sysctl(8). BSD
December 24, 2008 BSD
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