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Full Discussion: difference between == and =
Top Forums UNIX for Dummies Questions & Answers difference between == and = Post 302074128 by Corona688 on Saturday 20th of May 2006 02:37:33 AM
Old 05-20-2006
UNIX is an operating system, not a commandline. You seem to be talking about the standard UNIX shell, sh or one of it's clones like bash, but could have as easily been using something like korn... or even been programming in C.... = and == are pretty common.

I've never seen code like your first example, probably because it doesn't work. ( ) brackets aren't statement grouping, they define arrays!
Code:
arr=(a = c)
echo ${arr[0]}
echo ${arr[1]}
echo ${arr[2]}

will print a, then =, then c. The = isn't even treated as an operator inside the ().

Inside the [[ ]] brackets, == is a pattern matching operator for strings, and = is a straight equality comparison. Outside of there, = is an assignment operator like variable="something" and I don't think == does anything.

Also, your if statements aren't quite right. Try this:

Code:
if [[ $this = "that" ]]
then
      echo "Something"
else
      echo "Something else"
fi

Last edited by Corona688; 05-20-2006 at 03:47 AM..
 

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LEARN ABOUT SUNOS

cpc_event_accum

cpc_event_diff(3CPC)													      cpc_event_diff(3CPC)

NAME

       cpc_event_diff, cpc_event_accum - simple difference and accumulate operations

SYNOPSIS

       cc [ flag... ] file... -lcpc [ library... ]
       #include <libcpc.h>

       void cpc_event_accum(cpc_event_t *accum, cpc_event_t *event);

       void cpc_event_diff(cpc_event_t *diff, cpc_event_t *after, cpc_event_t *before);

       The  cpc_event_accum()  and  cpc_event_diff() functions	perform common accumulate and difference operations on cpc_event(3CPC) data struc-
       tures. Use of these functions increases program portability, since structure members are not referenced directly .

   cpc_event_accum()
       The cpc_event_accum() function adds the ce_pic fields of event into the corresponding fields of accum. The ce_hrt field of accum is set	to
       the later of the times in event and accum.

   SPARC:
       The function adds the contents of the ce_tick field of event into the corresponding field of accum.

   :
       The function adds the contents of the ce_tsc field of event into the corresponding field of accum.

   cpc_event_diff()
       The  cpc_event_diff()  function	places	the  difference between the ce_pic fields of after and before and places them in the corresponding
       field of diff. The ce_hrt field of diff is set to the ce_hrt field of after.

   SPARC:
       Additionally, the function computes the difference between the ce_tick fields of after and before, and places it in the corresponding field
       of diff.

   :
       Additionally,  the function computes the difference between the ce_tsc fields of after and before, and places it in the corresponding field
       of diff.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Obsolete			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

       cpc(3CPC), cpc_buf_add(3CPC), cpc_buf_sub(3CPC), cpc_event(3CPC), libcpc(3LIB), attributes(5)

       The cpc_event_accum() and cpc_event_diff() functions exist for binary compatibility only. Source containing these functions will  not  com-
       pile.  These  functions	are  obsolete  and  might  be  removed	in  a  future  release.  Applications  should  use  cpc_buf_add(3CPC)  and
       cpc_buf_sub(3CPC) instead.

								    28 Mar 2005 					      cpc_event_diff(3CPC)
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