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1) This is pager or swapper: Which process has PID 0? 2) Never used Minix but manual says negative pid in Minix means kernel process. As this is actually part of the kernel implementation, I can't say if that comply or not to POSIX =) 3) You should use pid_t If your aim is maximum portability you should read POSIX and it says: First, getpid() function ...


1

Given the command in your example, echo will run, but what happens to $APPLE is a little more complicated. It is true, as is indicated in @Patrick's answer here, that if the shell invokes a process all variables declared on the command-line preceding its invocation are specified to be exported into its environment. And further, those variables are also ...


8

As far as I can tell, the use of -- as end-of-options-marker starts with sh and getopt in System III Unix (1980). According to this history of the Bourne Shell family, the Bourne Shell first appeared in Version 7 Unix (1979). But it didn't have a way for set to separate options from arguments. So the original Bourne shell could do: set -e - turn on ...


2

Note GNU coreutils man pages are generated from $cmd --help Also note that bash builtins at least don't support --help. There you need to use help umask for example. Now POSIX allows, and ksh at least uses umask --help. It was proposed recently that bash might also accept this syntax


4

You refer to the GNU tools in your example. These are available on Linux, and many other platforms, and are somewhat unusual in terms of documentation. The GNU tools, actually seem to have three levels of increasingly detailed interactive reference: --help as a common command option - a short usage summary, man - the classic man pages, a "quick ...


4

Commercial unices generally present usage information only in man pages. Having the command itself display usage information is not a traditional Unix feature (except for displaying the list of supported options, but without any explanation, on a usage error). POSIX and its relatives don't talk about anything like this. Having a --help option that displays ...


4

POSIX general defines three special files: /dev/tty /dev/console /dev/null In addition, / and /tmp are also defined by POSIX. /dev/zero, /dev/urandom or /dev/random are defined in some UNIX-like operating systems. Some operating systems may not define them, or implement with different names. Note POSIX direcory structure and files /dev/zero ...



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