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Full Discussion: if statement negation
Top Forums Shell Programming and Scripting if statement negation Post 302498536 by Scrutinizer on Monday 21st of February 2011 05:55:11 PM
Old 02-21-2011
Also in square brackets in bash and ksh93 double == are preferred for a string comparison in combination with double brackets..
Code:
if ! [[ $x == 0 && $y == 0 ]]; then

Numerical comparison:
Code:
if ! [[ $x -eq 0 && $y -eq 0 ]]; then

Arithmetic evaluation:
Code:
if ! (( x == 0 && y == 0 )); then

Or POSIX tests (works in many other shells):
Code:
if ! ( [ "$x" = 0 ] && [ "$y" = 0 ] ) ; then

Code:
if ! ( [ $x -eq 0 ] && [ $y -eq 0 ] ) ; then


Last edited by Scrutinizer; 02-21-2011 at 07:09 PM..
 

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assert(3C)																assert(3C)

NAME
assert - verify program assertion SYNOPSIS
#include <assert.h> void assert(int expression); The assert() macro inserts diagnostics into applications. When executed, if expression is FALSE (zero), assert() prints the error message Assertion failed: expression, file xyz, line nnn on the standard error output and aborts. In the error message, xyz is the name of the source file and nnn the source line number of the assert() statement. These are respectively the values of the preprocessor macros __FILE__ and __LINE__. Since assert() is implemented as a macro, the expression may not contain any string literals. Compiling with the preprocessor option -DNDEBUG (see cc(1B)), or with the preprocessor control statement #define NDEBUG ahead of the #include <assert.h> statement, will stop assertions from being compiled into the program. Messages printed from this function are in the native language specified by the LC_MESSAGES locale category. See setlocale(3C). See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Safe | +-----------------------------+-----------------------------+ cc(1B), abort(3C), gettext(3C), setlocale(3C), attributes(5), standards(5) 30 Mar 2005 assert(3C)
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