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Meaning of this line in script

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# 1  
Old 01-22-2009
Meaning of this line in script
Can anyone explain me the meaning of line #2 in these lines of shell script:

if [ "${PMON}" == "yes" ] ; then
${EXPR} " ${MACTIONS[*]} " : ".* ${ACTION} " >/dev/null 2>&1 || die "$USAGE"
else

Sorry in case this is a trivial thing (I am not an expert in this).
# 2  
Old 01-22-2009
Translated roughly :
if variable PMON holds value 'yes', then execute the following : variables that do something, and : the first part, "> /dev/null" means send standard output away. The second part, "2>&1" means "redirect standard error (2) to the same place as standard output (1.) OR finish the execution of the script with printing the USAGE message.
# 3  
Old 01-22-2009
I particularly want to know the meaning of colon : and .* in the line. Can you pls explain ?
# 4  
Old 01-22-2009
Easiest thing to do is echo the line to see how it's expanded by the script, so just mod your program to...

Code:
if [ "${PMON}" == "yes" ] ; then
echo ${EXPR} " ${MACTIONS[*]} " : ".* ${ACTION} " 
${EXPR} " ${MACTIONS[*]} " : ".* ${ACTION} " >/dev/null 2>&1 || die "$USAGE"
else

and see what you get, but : is a 'null command' that always returns success and is used as a comment identifier.

Jerry
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