12-18-2018
Question about global environment variables & fork() exec()
Hello... And thanks in advance for any help anyone can offer me on my question! I've been doing a lot of reading to try and find my answer... But I haven't had any luck
What I'm trying to understand is where a child process inherits global environment variables from? I understand the exec() system call overwrites environment variable created by the fork()... But how does exec() cause global environment variables to be included with a newly created child process if all the environment variables are overwritten? My best guess is that global environment variables are somehow excluded from being overwritten... But I can't confirm this
Also... when does the fork() assign a PID to a child process? Before or after it copies itself into a new region of memory?
Thanks to everyone for any assistance!
Last edited by bodisha; 12-18-2018 at 04:21 PM..
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LEARN ABOUT DEBIAN
ns_execargv
Ns_Exec(3aolserver) AOLserver Library Procedures Ns_Exec(3aolserver)
__________________________________________________________________________________________________________________________________________________
NAME
Ns_ExecArgblk, Ns_ExecArgv, Ns_ExecProc, Ns_ExecProcess, Ns_Fork, Ns_GetEnviron, Ns_WaitForProcess, Ns_WaitProcess, ns_fork - External
process execution
SYNOPSIS
#include "ns.h"
int
Ns_ExecArgblk(char *exec, char *dir, int fdin, int fdout,
char *args, Ns_Set *env)
int
Ns_ExecArgv(char *exec, char *dir, int fdin, int fdout,
char **argv, Ns_Set *env)
int
Ns_ExecProc(char *exec, char **argv)
int
Ns_ExecProcess(char *exec, char *dir, int fdin, int fdout,
char *args, Ns_Set *env)
int
Ns_Fork(void)
char
**Ns_GetEnviron(void)
int
Ns_WaitForProcess(int pid, int *statusPtr)
int
Ns_WaitProcess(int pid)
int
ns_fork(void)
_________________________________________________________________
DESCRIPTION
These functions handle fork and exec operations. See files: nsd/exec.c, nsd/tclenv.c and nsthread/fork.c.
Ns_ExecArgblk(exec, dir, fdin, fdout, args, env)
Executes a command in a child process. Return process id of child process exec'ing the command or -1 on failure. Provides extended
error checking and error messages.
Ns_ExecArgv(exec, dir, fdin, fdout, argv, env)
Execute a command in a child process using fork(2) and execve(2), returns the process id of child process exec'ing the command or -1
on failure. The child sends an extended error message to the parent.
Ns_ExecProc(exec, argv)
Executes a command in a child process. Returns the process id of the child process exec'ing the command or -1 on failure. Simpli-
fies call to Ns_ExecArgv.
Ns_ExecProcess(exec, dir, fdin, fdout, args, env)
Executes a command in a child process. Returns the process id of the child process exec'ing the command or -1 on failure. Calls
Ns_ExecArgblk with same arguments.
Ns_Fork()
Posix style fork(), using fork1() on Solaris if needed. See fork(2) man page. Calls ns_fork.
Ns_GetEnviron()
Returns pointer to the environment vector.
Ns_WaitForProcess(pid, statusPtr)
Wait for child process. Returns NS_OK on success, or NS_ERROR on failure. *statusPtr is set to the exit code of the child process.
Ns_WaitProcess(pid)
Wait for child process. Calls Ns_WaitForProcess with NULL statusPtr. Returns NS_OK on success, or NS_ERROR on failure.
ns_fork()
Posix style fork(), using fork1() on Solaris if needed.
SEE ALSO
nsd(1), info(n)
KEYWORDS
AOLserver 4.0 Ns_Exec(3aolserver)