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Top Forums Shell Programming and Scripting Rules with using double parentheses in Bash Post 302495150 by cfajohnson on Wednesday 9th of February 2011 12:00:54 PM
Old 02-09-2011
Quote:
Originally Posted by lio123
Hi.could you explain me what are the rules when we are using double parentesis in if statement,if I put [ $# > 0 ],the code is working

That doesn't do what you think it does. (I made the same mistake when I first started shell scripting.)

The greater-than symbol, >, is a redirection operator, not a comparison operator (unless it is escaped, in which case it is string comparison, not numerical). What you need is:
Code:
[ $# -gt 0 ]

(I never use the non-standard (( ... )) syntax.)
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MESSAGES(3)						  libbash messages Library Manual					       MESSAGES(3)

NAME
messages -- libbash library that implements a set of functions to print standard status messages SYNOPSIS
printOK [indent] printFAIL [indent] printNA [indent] printATTN [indent] printWAIT [indent] DESCRIPTION
General messages is a collection of functions to print standard status messages - those [ OK ] and [FAIL] messages you see during Linux boot process. The function list: printOK Prints a standard [ OK ] message (green) printFAIL Prints a standard [FAIL] message (red) printNA Prints a standard [ N/A] message (yellow) printATTN Prints a standard [ATTN] message (yellow) printWAIT Prints a standard [WAIT] message (yellow) Detailed interface description follows. indent Column to move to before printing. Default indent is calculated as TTY_WIDTH-10. If current tty width can not be determined (for example, in case of serial console), it defaults to 80, so default indent is 80-10=10 FUNCTIONS DESCRIPTIONS
printOK [indent] Prints a standard [ OK ] message (green) printFAIL [indent] Prints a standard [FAIL] message (red) printNA [indent] Prints a standard [ N/A] message (yellow) printATTN [indent] Prints a standard [ATTN] message (yellow) printWAIT [indent] Prints a standard [WAIT] message (yellow) EXAMPLES
Run a program named MyProg, and report it's success or failure: echo -n 'Running MyProg...' printWAIT if MyProg ; then printOK else printFAIL fi AUTHORS
Hai Zaar <haizaar@haizaar.com> Gil Ran <gil@ran4.net> SEE ALSO
ldbash(1), libbash(1) Linux Epoch Linux
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