execve 中文man頁面

作者：徐明 2011-08-25 14:10:47

execve() 執行 filename 指出的程序. filename 必須是二進制可執行文件, 或者以 "#! interpreter [arg]" 行開始的腳本文件. 后者的 interpreter 必須是某個可執行文件的有效路徑, 這個可執行文件自身不能是腳本程序, 調用形式是 "interpreter [arg] filename".

NAME

execve - 執行程序

總覽 (SYNOPSIS)

#include <unistd.h>

int execve (const char *filename, char *const argv [], char *const envp[]);

描述 (DESCRIPTION)

execve() 執行 filename 指出的程序. filename 必須是二進制可執行文件, 或者以 "#! interpreter [arg]" 行開始的腳本文件. 后者的 interpreter 必須是某個可執行文件的有效路徑, 這個可執行文件自身不能是腳本程序, 調用形式是 "interpreter [arg] filename".

execve() 調用成功后不會返回, 其進程的正文(text), 數據(data), bss 和堆棧(stack) 段被調入程序覆蓋. 調入程序繼承了調用程序的 PID 和所有打開的文件描述符, 他們不會因為 exec 過程而關閉. 父進程的未決信號被清除. 所有被調用進程設置過的信號重置為缺省行為.

如果當前程序正在被 ptrace 跟蹤, 成功的調用 execve() 后將收到一個 SIGTRAP 信號.

如果可執行文件是動態連接的 a.out 二進制程序, 含有共享庫的 stub, 開始執行程序的時候, Linux 動態連接器(linker) ld.so(8) 把所需的共享庫調入核心, 并且和程序相連.

如果可執行文件是動態連接的 ELF 二進制程序, 定義在 PT_INTERP 字段的解釋器(interpreter) 調入所需的共享庫. 連接 libc5 的程序的典型解釋器是 /lib/ld-linux.so.1, 而連接 GNU libc2 (libc6) 的程序則為 /lib/ld-linux.so.2.

返回值 (RETURN VALUE)

調用成功的時候 execve() 不會返回, 調用失敗時返回 -1, 并設置 errno 為相應的值.

錯誤 (ERRORS)

EACCES: 文件或腳本解釋器不正確.
EACCES: 沒有文件或腳本解釋器的執行權限.
EACCES: 文件系統掛載(mount) 為 noexec.
EPERM: 文件系統掛載為 nosuid, 使用者不是超級用戶, 以及文件設置了 SUID 或 SGID 位.
EPERM: 進程正被跟蹤, 使用者不是超級用戶, 以及文件設置了 SUID 或 SGID 位.
E2BIG: 參數列表過長.
ENOEXEC: 可執行文件的文件格式無法識別, 誤用在不同的體系結構, 或者其他格式錯誤導致程序無法執行.
EFAULT: filename 指針超出可訪問的地址空間.
ENAMETOOLONG: filename 太長.
ENOENT: filename , 腳本解釋器, 或 ELF 解釋器不存在.
ENOMEM: 內核空間不足.
ENOTDIR: 在 filename , 腳本解釋器或 ELF 解釋器的前綴路徑中, 某些成員不是目錄.
EACCES: 在 filename 或腳本解釋器的前綴路徑中, 對某些目錄沒有訪問許可.
ELOOP: 解析 filename , 腳本解釋器或 ELF 解釋器時遇到過多的符號連接.
ETXTBUSY: 可執行文件被一個或多個進程以寫方式打開.
EIO: 發生 I/O 錯誤.
ENFILE: 達到系統定義的同時打開文件數限制.
EMFILE: 進程打開了最大數量的文件.
EINVAL: 該 ELF 可執行文件擁有多個 PT_INTERP 字段 (就是說, 試圖定義多個解釋器).
EISDIR: ELF 解釋器是目錄.
ELIBBAD: 無法識別 ELF 解釋器的格式.

CONFORMING TO

SVr4, SVID, X/OPEN, BSD 4.3. POSIX 沒有對 #! 行為的文檔, 但有其他的兼容形式. SVr4 記錄了額外的錯誤情況 EAGAIN, EINTR, ELIBACC, ENOLINK, EMULTIHOP; POSIX 沒有關于 ETXTBSY, EPERM, EFAULT, ELOOP, EIO, ENFILE, EMFILE, EINVAL, EISDIR 或 ELIBBAD 錯誤情況的文檔.

注意 (NOTES)

SUID and SGID processes can not be ptrace()d SUID or SGID.

在 #! 格式的 shell 可執行腳本中, 第一行的長度不得超過 127 字節.

Linux 忽略腳本程序的 SUID 和 SGID 位.

另見 (SEE ALSO)

ld.so(8), execl(3), fork(2)

#p#

NAME

execve - execute program

SYNOPSIS

#include <unistd.h>

int execve(const char *filename, char *const argv [], char *const envp[]);

DESCRIPTION

execve() executes the program pointed to by filename. filename must be either a binary executable, or a script starting with a line of the form "#! interpreter [arg]". In the latter case, the interpreter must be a valid pathname for an executable which is not itself a script, which will be invoked as interpreter [arg] filename.

argv is an array of argument strings passed to the new program. envp is an array of strings, conventionally of the form key=value, which are passed as environment to the new program. Both argv and envp must be terminated by a null pointer. The argument vector and environment can be accessed by the called program's main function, when it is defined as int main(int argc, char *argv[], char *envp[]).

execve() does not return on success, and the text, data, bss, and stack of the calling process are overwritten by that of the program loaded. The program invoked inherits the calling process's PID, and any open file descriptors that are not set to close on exec. Signals pending on the calling process are cleared. Any signals set to be caught by the calling process are reset to their default behaviour. The SIGCHLD signal (when set to SIG_IGN) may or may not be reset to SIG_DFL.

If the current program is being ptraced, a SIGTRAP is sent to it after a successful execve().

If the set-uid bit is set on the program file pointed to by filename the effective user ID of the calling process is changed to that of the owner of the program file. Similarly, when the set-gid bit of the program file is set the effective group ID of the calling process is set to the group of the program file.

If the executable is an a.out dynamically-linked binary executable containing shared-library stubs, the Linux dynamic linker ld.so(8) is called at the start of execution to bring needed shared libraries into core and link the executable with them.

If the executable is a dynamically-linked ELF executable, the interpreter named in the PT_INTERP segment is used to load the needed shared libraries. This interpreter is typically /lib/ld-linux.so.1 for binaries linked with the Linux libc version 5, or /lib/ld-linux.so.2 for binaries linked with the GNU libc version 2.

RETURN VALUE

On success, execve() does not return, on error -1 is returned, and errno is set appropriately.

ERRORS

EACCES: The file or a script interpreter is not a regular file.
EACCES: Execute permission is denied for the file or a script or ELF interpreter.
EACCES: The file system is mounted noexec.
EPERM: The file system is mounted nosuid, the user is not the superuser, and the file has an SUID or SGID bit set.
EPERM: The process is being traced, the user is not the superuser and the file has an SUID or SGID bit set.
E2BIG: The argument list is too big.
ENOEXEC: An executable is not in a recognised format, is for the wrong architecture, or has some other format error that means it cannot be executed.
EFAULT: filename points outside your accessible address space.
ENAMETOOLONG: filename is too long.
ENOENT: The file filename or a script or ELF interpreter does not exist, or a shared library needed for file or interpreter cannot be found.
ENOMEM: Insufficient kernel memory was available.
ENOTDIR: A component of the path prefix of filename or a script or ELF interpreter is not a directory.
EACCES: Search permission is denied on a component of the path prefix of filename or the name of a script interpreter.
ELOOP: Too many symbolic links were encountered in resolving filename or the name of a script or ELF interpreter.
ETXTBSY: Executable was open for writing by one or more processes.
EIO: An I/O error occurred.
ENFILE: The limit on the total number of files open on the system has been reached.
EMFILE: The process has the maximum number of files open.
EINVAL: An ELF executable had more than one PT_INTERP segment (i.e., tried to name more than one interpreter).
EISDIR: An ELF interpreter was a directory.
ELIBBAD: An ELF interpreter was not in a recognised format.

CONFORMING TO

SVr4, SVID, X/OPEN, BSD 4.3. POSIX does not document the #! behavior but is otherwise compatible. SVr4 documents additional error conditions EAGAIN, EINTR, ELIBACC, ENOLINK, EMULTIHOP; POSIX does not document ETXTBSY, EPERM, EFAULT, ELOOP, EIO, ENFILE, EMFILE, EINVAL, EISDIR or ELIBBAD error conditions.

NOTES

SUID and SGID processes can not be ptrace()d.

Linux ignores the SUID and SGID bits on scripts.

The result of mounting a filesystem nosuid vary between Linux kernel versions: some will refuse execution of SUID/SGID executables when this would give the user powers she did not have already (and return EPERM), some will just ignore the SUID/SGID bits and exec successfully.

A maximum line length of 127 characters is allowed for the first line in a #! executable shell script.

HISTORICAL

With Unix V6 the argument list of an exec call was ended by 0, while the argument list of main was ended by -1. Thus, this argument list was not directly usable in a further exec call. Since Unix V7 both are NULL.