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Top Forums Shell Programming and Scripting what does ${VARIABLE:-0} stand for? Post 302381824 by sleepy_11 on Monday 21st of December 2009 02:11:51 AM
Old 12-21-2009
Question what does ${VARIABLE:-0} stand for?

Hi all,

During reading the code, i met such expressment in a KSH script. I can not figure out what does this mean and don't know how to search it in the web. Could you please check below snippet and let me know what does this mean in a shell script:

Code:
VARIABLE=1
if [ ${VARIABLE:-0} -ne 1 ]; then
   . /bin/another_shell.sh
fi

I also met similiar situation before like:
Code:
${VARIABLE:-1}
${VARIABLE:-0/}

(may not exaclty like it, but there is definitely a slash at the end)

Thanks in Adv.

Last edited by zaxxon; 12-21-2009 at 03:44 AM.. Reason: use code tags please
 

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CTL(5)						    CTL file format of ASIM/LIP6/CAO-VLSI lab.						    CTL(5)

NAME
ctl - Control Temporal Logic file format. ORIGIN
This software belongs to the ALLIANCE CAD SYSTEM developed by the ASIM team at LIP6 laboratory of Universite Pierre et Marie CURIE, in Paris, France. Web : http://asim.lip6.fr/recherche/alliance/ E-mail : alliance-users@asim.lip6.fr DESCRIPTION
This document describes the CTL file format used by moka(1) for model checking of finite states machine description. This CTL file format subset is defined to enable classical CTL formulae description. A CTL file is made of two parts: a declaration part and a formulae statement part. The declaration part described types, constants, macros and all variables used in CTL formulae. It also describes assumption conditions and initial conditions that have to be applied by moka(1) during the model checking. The formulae statement part described all the CTL formulae that have to be verified. All boolean and relational VHDL operators are supported (see vbe(5)) and also the 8 CTL operators AF, AG, AX, AU, EF, EG, EX and EU. The CTL file format support also the imply boolean operator '->' and the equivalence operator '<=>'. EXAMPLE
-- user type definition TYPE A_ETAT_TYPE IS (A_E0, A_E1); TYPE B_ETAT_TYPE IS (B_E0, B_E1); -- variables definition VARIABLE A_NS, A_CS : A_ETAT_TYPE; VARIABLE B_NS, B_CS : B_ETAT_TYPE; VARIABLE ck : BIT; VARIABLE data_in : BIT; VARIABLE data_out : BIT; VARIABLE reset : BIT; VARIABLE ack : BIT; VARIABLE req : BIT; -- example of a macros definition DEFINE def1 : BOOLEAN := ack='1'; -- the assigned value can be a constant DEFINE c1 : BIT := '1'; -- the assumption condition ASSUME ass1 := (reset='0'); -- the initial reset condition -- be careful, the assumption condition is not applied -- to the initial conditions. RESET_COND init1 := (reset='1'); -- It is also possible to describe the first state -- with the INITIAL keywork, as follows: -- -- INITIAL init1 := ((A_CS=A_E0) AND (B_CS=B_E0)); -- -- formulae description statement part begin prop1 : EX( ack='1' ); prop2 : AG( req -> AF( ack ) ); prop4 : AU( req='1', ack='1'); end; SEE ALSO
moka(1) BUG REPORT
This tool is under development at the ASIM department of the LIP6 laboratory. We need your feedback to improve documentation and tools. ASIM
/LIP6 August 5, 2002 CTL(5)
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