add directory Minix

Minix/CD-ROM-2.0/MINIX/MANUALS/CAT3/EXECL.3

@@ -0,0 +1,118 @@
+
+
+EXECL(3)                  Minix Programmer's Manual                   EXECL(3)
+
+
+NAME
+     execl, execv, execle, execlp, execvp, exec, environ - execute a file
+
+SYNOPSIS
+     #include <unistd.h>
+
+     int execl(const char *name, const char *arg0, ..., (char *) NULL)
+     int execv(const char *name, char *const argv[])
+     int execle(const char *name, const char *arg0, ..., (char *)  NULL,  char
+           *const envp[])
+     int execlp(const char *name, const char *arg0, ..., (char *) NULL)
+     int execvp(const char *name, char *const argv[])
+
+     extern char *const *environ;
+
+DESCRIPTION
+     These routines provide various interfaces  to  the  execve  system  call.
+     Refer  to  execve(2)  for  a  description of their properties; only brief
+     descriptions are provided here.
+
+     Exec in all its forms overlays the calling process with the  named  file,
+     then  transfers  to the entry point of the core image of the file.  There
+     can be no return from a successful exec; the calling core image is lost.
+
+     The name argument is a pointer to the name of the file  to  be  executed.
+     The   pointers  arg[0],  arg[1]  ...   address  null-terminated  strings.
+     Conventionally arg[0] is the name of the file.
+
+     Two interfaces are available.  execl is useful when  a  known  file  with
+     known arguments is being called; the arguments to execl are the character
+     strings constituting the file and the arguments; the  first  argument  is
+     conventionally the same as the file name (or its last component).  A null
+     pointer argument must end the  argument  list.   (Note  that  the  execl*
+     functions  are  variable argument functions.  This means that the type of
+     the arguments beyond arg0 is not checked.  So the null  pointer  requires
+     an explicit cast to type (char *) if not of that type already.)
+
+     The execv version is useful when the number of arguments  is  unknown  in
+     advance;  the  arguments to execv are the name of the file to be executed
+     and a vector of strings containing  the  arguments.   The  last  argument
+     string must be followed by a null pointer.
+
+     When a C program is executed, it is called as follows:
+
+          int main(int argc, char *const argv[], char *const envp[]);
+
+          exit(main(argc, argv, envp));
+
+
+
+
+
+5BSD                             April 25, 1986                              1
+
+
+
+EXECL(3)                  Minix Programmer's Manual                   EXECL(3)
+
+
+     where argc is the argument count  and  argv  is  an  array  of  character
+     pointers   to   the   arguments   themselves.    As  indicated,  argc  is
+     conventionally at least one and the first member of the array points to a
+     string containing the name of the file.
+
+     Argv is directly usable in another execv because argv[argc] is 0.
+
+     Envp is a pointer to an array of strings that constitute the  environment
+     of  the  process.   Each  string  consists of a name, an "=", and a null-
+     terminated value.  The array of pointers is terminated by a null pointer.
+     The  shell  sh(1)  passes  an  environment  entry  for  each global shell
+     variable defined when the program is called.   See  environ(7)  for  some
+     conventionally  used  names.   The  C run-time start-off routine places a
+     copy of envp in the global cell environ, which is used by execv and execl
+     to  pass  the  environment  to  any  subprograms  executed by the current
+     program.
+
+     Execlp and execvp are called with the same arguments as execl and  execv,
+     but  duplicate the shell's actions in searching for an executable file in
+     a  list  of  directories.   The  directory  list  is  obtained  from  the
+     environment variable PATH.  Under standard Minix, if a file is found that
+     is executable, but does not have the proper executable header then it  is
+     assumed  to  be  a  shell  script.   Execlp and execvp execute /bin/sh to
+     interpret the script.  Under Minix-vmd this does  not  happen,  a  script
+     must  begin with #! and the full path name of the interpreter if it is to
+     be an executable script.
+
+SEE ALSO
+     execve(2), fork(2), environ(7), sh(1).
+
+DIAGNOSTICS
+     If the file cannot be found, if it is not  executable,  if  it  does  not
+     start  with  a  valid  magic  number (see a.out(5)), if maximum memory is
+     exceeded,  or  if  the  arguments  require  too  much  space,  a   return
+     constitutes  the  diagnostic;  the return value is -1 and errno is set as
+     for execve.  Even for the  super-user,  at  least  one  of  the  execute-
+     permission bits must be set for a file to be executed.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+5BSD                             April 25, 1986                              2
+