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SHMCAT(1)		    General Commands Manual		     SHMCAT(1)

NAME
       shmcat -	dump shared memory segments, files, standard input and/or text

SYNOPSIS
       shmcat [	OPTION ]... [ OPERAND ]...

DESCRIPTION
       Dump shared memory segments, files, standard input and/or text to stan-
       dard output. If no OPERAND is given, read standard input	only. If  more
       than  one OPERAND is given, dump	them in	order. If some of the OPERANDs
       cannot be read, shmcat prints an	error message to  standard  error  and
       tries  to continue with the other OPERANDs, unless the -S or --stop op-
       tion is given.

       Most modern systems support two APIs for	shared memory:

       The older one is	commonly known as the System V API.  It	 uses  numeric
       keys  and  IDs  as  identifiers	and  consists  of  system  calls  like
       shmget(2), shmat(2) and shmdt(2).

       The newer API is	called the POSIX shared	memory API. It uses  names  in
       string  form  as	identifiers. It	treats shared memory similar to	files,
       which are opened	with shm_open(3) and then mapped into the program  ad-
       dress  space  via  mmap(2). Please note that POSIX shared memory	is not
       supported by all	versions of shmcat.

       If shmcat has been compiled without getopt_long(3)  support,  only  the
       short,  one  character  OPTIONs and OPERANDs can	be used. Otherwise the
       long ones are also available. When a long OPTION	or  OPERAND  needs  an
       argument, the short versions do so, as well.

OPTIONS
       -h, -?, --help
	      Display usage information	and quit without dumping anything.

       -S, --stop
	      By  default,  if an OPERAND cannot be read, shmcat tries to con-
	      tinue with the remaining OPERANDs. This option turns of that be-
	      havior,  so  that	 the program stops immediately after the first
	      OPERAND that cannot be read.

       -V, --version
	      Show version information and quit	without	further	action.

OPERANDS
       -f, --file=FILENAME
	      Dump the contents	of the given file.

       -i, --stdin
	      Dump standard input.

       -M, --shmkey=KEY
	      Dump the System V	shared memory segment with the given key.  The
	      key  can be given	as a decimal (no prefix), octal	(prefix	0), or
	      hexadecimal (prefix 0x) number. It can, for example, be obtained
	      using the	ipcs(1)	or the ftok(1) tool.

       -m, --shmid=ID
	      Dump  the	 System	V shared memory	segment	with the given id. The
	      id can be	given as a decimal (no prefix),	octal (prefix  0),  or
	      hexadecimal (prefix 0x) number. It can, for example, be obtained
	      using the	ipcs(1)	tool.

       -n, --newline
	      Add a line feed.

       -p, --posix-shm=NAME
	      Dump the POSIX shared memory segment with	the  given  name  (not
	      supported	in all installations).

       -t, --text=TEXT
	      Print the	given text.

EXIT CODES
       0      No errors, every OPERAND requested was dumped.

       1      There  was  an error while opening or reading at least one OPER-
	      AND. If shmcat has been invoked with the -S  or  --stop  option,
	      the program stopped after	this error, otherwise it tried to con-
	      tinue with the remaining OPERANDs	(if given).

       2      There was	a fatal	error, usually this means  that	 shmcat	 could
	      not write	to standard output.

       10     Wrong usage of the program.

NOTES
       Usually,	 when you dump shared memory segments, you should redirect the
       output of shmcat	to a file or a program like od(1), because shared mem-
       ory  data  usually has a	binary form and	thus it	may contain non-print-
       able characters.	You also probably want to suspend the processes	 writ-
       ing to the shared memory	object in order	to get a consistent dump.

AUTHOR
       Stefan Gast

SEE ALSO
       ftok(1),	ipcs(1), shmat(2), shmget(2), shm_open(3)

shmcat(1)			  August 2016			     SHMCAT(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | EXIT CODES | NOTES | AUTHOR | SEE ALSO

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