NAME

execve - 執(zhí)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(zhí)行 filename 指出的 程序. filename 必須 是二進(jìn)制可執(zhí)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(gè) 可執(zhí)行文件 的 有效 路徑, 這個(gè) 可執(zhí)行文件 自身不能是 腳本程序, 調(diào)用 形式 是 "interpreter [arg] filename".

execve() 調(diào)用 成功 后 不會(huì) 返回, 其 進(jìn)程 的 正文(text), 數(shù)據(jù)(data), bss 和 堆棧(stack) 段 被 調(diào)入程序 覆蓋. 調(diào)入程序 繼承了 調(diào)用程序 的 PID 和所有 打開的 文件描述符, 他們 不會(huì) 因?yàn)?exec 過程 而 關(guān)閉. 父進(jìn)程 的 未決 信號(hào)被 清除. 所有 被 調(diào)用進(jìn)程 設(shè)置過 的 信號(hào) 重置為 缺省行為.

如果 當(dāng)前程序 正在 被 ptrace 跟蹤, 成功的 調(diào)用 execve() 后 將 收到一個(gè) SIGTRAP 信號(hào).

如果 可執(zhí)行文件 是 動(dòng)態(tài)連接 的 a.out 二進(jìn)制程序, 含有 共享庫 的 stub, 開始 執(zhí)行 程序 的 時(shí)候, Linux 動(dòng)態(tài) 連接器(linker) ld.so(8) 把 所需的 共享庫 調(diào)入 核心, 并且 和 程序 相連.

如果 可執(zhí)行文件 是 動(dòng)態(tài)連接 的 ELF 二進(jìn)制程序, 定義在 PT_INTERP 字段 的解釋器(interpreter) 調(diào)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(diào)用成功 的 時(shí)候 execve() 不會(huì) 返回, 調(diào)用失敗 時(shí) 返回 -1, 并 設(shè)置 errno 為 相應(yīng)的 值.

錯(cuò)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(zhí)行 權(quán)限.

EACCES

文件系統(tǒng) 掛載(mount) 為 noexec.

EPERM

文件系統(tǒng) 掛載為 nosuid, 使用者 不是 超級(jí)用戶, 以及 文件 設(shè)置了 SUID 或 SGID 位.

EPERM

進(jìn)程 正 被跟蹤, 使用者 不是 超級(jí)用戶, 以及 文件 設(shè)置了 SUID 或 SGID 位.

E2BIG

參數(shù)列表 過長(zhǎng).

ENOEXEC

可執(zhí)行文件 的 文件格式 無法 識(shí)別, 誤用在 不同的 體系結(jié)構(gòu), 或者 其他 格式錯(cuò)誤 導(dǎo)致 程序 無法 執(zhí)行.

EFAULT

filename 指針 超出 可訪問 的 地址空間.

ENAMETOOLONG

filename 太長(zhǎng).

ENOENT

filename , 腳本解釋器, 或 ELF 解釋器 不存在.

ENOMEM

內(nèi)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(duì) 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(shí) 遇到 過多的 符號(hào)連接.

ETXTBUSY

可執(zhí)行文件 被 一個(gè) 或 多個(gè) 進(jìn)程 以 寫方式 打開.

EIO

發(fā)生 I/O 錯(cuò)誤.

ENFILE

達(dá)到 系統(tǒng) 定義的 同時(shí)打開文件數(shù) 限制.

EMFILE

進(jìn)程 打開了 最大數(shù)量 的 文件.

EINVAL

該 ELF 可執(zhí)行文件 擁有 多個(gè) PT_INTERP 字段 (就是說, 試圖 定義 多個(gè) 解釋器).

EISDIR

ELF 解釋器 是 目錄.

ELIBBAD

無法 識(shí)別 ELF 解釋器 的 格式.

CONFORMING TO

SVr4, SVID, X/OPEN, BSD 4.3. POSIX 沒有 對(duì) #! 行為 的 文檔, 但有 其他的兼容 形式. SVr4 記錄了 額外的 錯(cuò)誤情況 EAGAIN, EINTR, ELIBACC, ENOLINK, EMULTIHOP; POSIX 沒有 關(guān)于 ETXTBSY, EPERM, EFAULT, ELOOP, EIO, ENFILE, EMFILE, EINVAL, EISDIR 或 ELIBBAD 錯(cuò)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(zhí)行腳本 中, 第一行 的 長(zhǎng)度 不得 超過 127 字節(jié).

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.

SEE ALSO

chmod(2), fork(2), execl(3), environ(5), ld.so(8)