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Top Forums UNIX for Beginners Questions & Answers Shell script to check a command executed sucessfully or not Post 303043490 by Scrutinizer on Wednesday 29th of January 2020 04:12:00 PM

Looking at this snippet:

$? will always be true (0) since the previous command is xyz="$abc" which is a variable assignment, which will always be successful..
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kvar(8) 						      System Manager's Manual							   kvar(8)

       kvar - modify RISC kernel variables in memory or on disk

       /usr/etc/kvar -r(b|w|l) [options] vmunix
       /usr/etc/kvar -w(b|w|l) [options] vmunix

       The  command  allows you to read or write RISC kernel variables, either in the on-disk image of or the active in-memory image.  The -r form
       of the command does variable reads; the -w form does variable writes.  The variable length qualifiers are:  b  (1  byte),  w  (word,  or  2
       bytes), and l (longword, or 4 bytes).

       Variable contents are displayed in hexadecimal format.

       -a address  Specifies  the  address  of	the  kernel  variable.	Either the -a or -s option must be specified.  The address is specified as
		   either a positive decimal or hexadecimal constant.

       -k	   Instructs to use the in-memory image of The default is to use the on-disk copy.

       -l	   Searches for a local symbol. The default is a global symbol search.

       -o offset   Adds an offset to the address (or address of the symbol name).  The offset value is specified as either a positive  decimal	or
		   hexadecimal constant.

       -s name	   Specifies the name of the kernel variable.

       -v value    Specifies  the  new value to be assigned by the -w form of The -v option is ignored if the -r form of is being used.  The value
		   is specified as either a positive decimal or hexadecimal constant.

       You must have appropriate file access permissions for (and for with the -k option).

       The command is available only on RISC systems.  For VAX systems, use to modify kernel variables.

       This example reads the variable `udpcksum' from the running kernel image:

	    % kvar -k -rl -s udpcksum /vmunix

       This example sets the `xyz' variable to zero in the running kernel image:

	      % kvar -k -wl -s xyz -v 0 /vmunix

       This example sets the variable `xyz' to -1 in the on-disk image of making this value persistent across reboots:

	      % kvar -wl -s xyz -v 0xffffffff /vmunix

       This example sets to zero 1 byte at offset 2 from address 0x80161a98 in the running kernel image:

	      % kvar -k -wb -o 2 -a 0x80161a98 /vmunix

See Also
       adb(1), dbx(1)

								       RISC								   kvar(8)

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