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Check this Wikipedia link on Exec function and this link on Starting a process with the exec() calls e – An array of pointers to environment variables is explicitly passed to the new process image. The "e" suffix versions pass an environment to the program. An environment is just that—a kind of "context" for the program to operate in. For example, ...


According to http://www.di.uevora.pt/~lmr/syscalls.html, the suffixes indicate the type of arguments: l argn is specified as a list of arguments. v argv is specified as a vector (array of character pointers). e environment is specified as an array of character pointers. p user's PATH is searched for command, and command can be a shell ...


Dennis Ritchie set himself a constraint with C that it wouldn't rely on any linker features that weren't also required by Fortran. Hence the 6 character limit on external names.


In addition to the other answers, I would like to point out that Unix was developed as a reaction to Multics, CTSS, and other contemporary operating systems, which were significantly more verbose about their naming conventions. You can get a feel for these OSes at http://www.multicians.org/devdoc.html. For example, ...


Because of how waitpid works. On a POSIX system, a signal (SIGCHLD) is delivered to a parent process when one of its child processes dies. At a high level, all waitpid is doing is blocking until a SIGCHLD signal is delivered for the process (or one of the processes) specified. You can't wait on arbitrary processes, because the SIGCHLD signal would never ...


dr01 is right, but there's also another reason - usability. Back in the day, you didn't have something as comfortable as a keyboard to type on. If you were lucky, you had something akin to an old-school typewriter. If you were unlucky, you had to deal with systems that required actual physical work to operate (as in, it took a lot of force to press the ...


It's due to the technical constraints of the time. The POSIX standard was created in the 1980s and referred to UNIX, which was born in the 1970. Several C compilers at that time were limited to identifiers that were 6 or 8 characters long, so that settled the standard for the length of variable and function names.

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