execv

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1^# BOoRFGOnZ 发表于 2008-02-21 16:01

execv

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Executes a file.

Syntax

#include <unistd.h>

int execv (const char *pathname, const char *argv[]);

Parameters

pathname		A pointer to a string containing the pathname of the executable filethat is to become the new process image. The pathname must beterminated by a null character. The elements of the pathname must be uppercase and must resolve to avalid MPE/iX file, group, and account. For example, the pathname /FINANCE/PAYROLL/JULY must resolve to JULY.PAYROLL.FINANCE, where JULY is an executable file located in MPE/iX group PAYROLL and MPE/iX account FINANCE.
argv		A pointer to an array where each element contains a pointer to a stringcontaining an argument to the new process image. Each argument must beterminated by a null character. The element following the last elementpointing to an argument must contain a NULL pointer. For an application to be strictly conforming, the first element, argv[0], must point to a string containing a filename that identifies the executable file for the new process image.

Return Values

No return		Success.
-1		An error occurred. The current process image remains unchanged, and errno is set to indicate the error condition.

Description

The execv() function replaces the current process image with a new process image created from the executable file specified by pathname.
Use the execl() function if you know the exact number of arguments to be passed to the new process image. Use the execv() function if the number of arguments passed to the new process image might vary at run time.
If the new process image is a C program, it is entered as a C function call having the following declaration:

int main (int argc, const char *argv[])

In the above declaration, argc is a count of the number of pointers in the array argv[]. The NULL pointer terminating argv[] is not counted in argc.
The environment for the new process image is identical to the environment of the calling process.
If the new process image is not a C program, no information is made available through the argument list in argv[].
The sum of the bytes used in both the argument list and environment list must not exceed {ARG_MAX} (defined in the file <limits.h>).
File descriptors open in the calling process image remain openin the new process image. For all file descriptors that remain open,all attributes of the open file description remain unchanged by thisfunction, including file locks.
Streams open in the calling process image are not accessible inthe new process image. (However, the underlying file descriptors thatremain open, but inaccessible, are counted towards {OPEN_MAX}.)
Signals set to SIG_DFL or SIG_IGNin the calling process remain unchanged in the new process image. Allsignals of the calling process whose action is to invoke a signalhandling function are set to SIG_DFL in the new process image.
The following attributes of the new process image are set to the same values of those of the calling process:

process ID
parent process ID
process group ID
session membership
real user ID
real group ID
time remaining until a SIGALRM signal
current working directory
root directory
file mode creation mask
process signal mask
pending signals
tms_utime, tms_stime, tms_cutime, and tms_cstime

The executable file's st_atime time field is marked for update. If the execv() function succeeds, the executable file is open until the new process image terminates or executes another of the exec() functions.

Implementation Considerations

Refer to the EPERM, EIMPL, and ENOEXEC error descriptions below.
Some MPE/iX process attributes that are not specified in the POSIX 1003.1 standard are not inherited by the new process image.
NULL terminators and pointers are counted against {ARG_MAX}.Alignment bytes are counted against {ARG_MAX}.
The calling process's privilege level is used as the new program's maximum privilege level.
If the calling process entered debug mode through the ;DEBUG option of the MPE/iX CI RUN command, the new process image is also in debug mode.

Errors

If an error occurs, errno is set to one of the following values:

E2BIG	CAUSE	The number of bytes used by the new process image's argument list and environment list combined is greater than the limit of {ARG_MAX} (defined in the file <limits.h>).
	ACTION	Reduce the size of the argument list or the environment list or both.
EACCES	CAUSE	One of the following: The calling process does not have search permission to a component of the pathname. The calling process does not have execute permission to the file. The file is not a valid executable file.
	ACTION	One of the following: Make sure that the calling process has search permission to all components of the pathname. Make sure that the calling process has execute permission to the file. Make sure that the file has an MPE/iX file code of NMPRG.
EFAULT	CAUSE	The system detected a NULL or bad address in attempting to use the pathname parameter, or the pathname was not terminated by a null character.
	ACTION	Make sure that the pointer is correctly initialized.
EIMPL	CAUSE	The pathname did not resolve to a valid MPE/iX file, group, and account.
	ACTION	Specify a valid pathname as described in the pathname parameter description.
ENAMETOOLONG	CAUSE	One of the following: The length of the pathname exceeds the {PATH_MAX} limit (defined in the file <limits.h>). A component of the pathname is longer than {NAME_MAX} (defined in <limits.h>), and {_POSIX_NO_TRUNC} is in effect for that directory.
	ACTION	Make sure that both the component's length and the full pathnamelength do not exceed the {NAME_MAX} or {PATH_MAX} limits.
ENOENT	CAUSE	A component of the pathname for the executable file does not exist, or pathname points to an empty string.
	ACTION	Specify a valid pathname.
ENOEXEC	CAUSE	The program file does not have the NMPRG file code.
	ACTION	Make sure that the program file has the NMPRG file code.
ENOMEM	CAUSE	The new process image requires more memory than the system allows.
	ACTION	No action required. The new process image cannot be created.
ENOTDIR	CAUSE	A component of the pathname is not a directory.
	ACTION	Specify a valid pathname.
EPERM	CAUSE	One of the following: The calling process does not have the MPE/iX process handling (PH) capability. Thecalling process has outstanding switches to CM code, has set criticalmode, has outstanding NOWAITIO, or is holding an operating systeminternal resource.
	ACTION	One of the following: Link the program file with the MPE/iX PH capability. Do not execute execl()when the calling process has outstanding switches to CM code, has setcritical mode, has outstanding NOWAITIO, or is holding an operatingsystem internal resource.