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EXECVEAT(2)                Linux Programmer's ManualEXECVEAT(2)NAME       execveat - execute program relative to a directory file descriptorSYNOPSIS       #include <unistd.h>       int execveat(int dirfd, const char *pathname,                    char *const argv[], char *const envp[],                    int flags);DESCRIPTION       The execveat() system call executes the program referred to by the com-       bination of dirfd and pathname.  It operates in exactly the same way asexecve(2), except for the differences described in this manual page.       If  the  pathname given in pathname is relative, then it is interpreted       relative to the directory referred to  by  the  file  descriptor  dirfd       (rather  than  relative to the current working directory of the calling       process, as is done byexecve(2) for a relative pathname).       If pathname is relative and dirfd is the special value  AT_FDCWD,  then       pathname  is  interpreted  relative to the current working directory of       the calling process (likeexecve(2)).       If pathname is absolute, then dirfd is ignored.       If pathname is an empty string and the AT_EMPTY_PATH flag is specified,       then the file descriptor dirfd specifies the file to be executed (i.e.,       dirfd refers to an executable file, rather than a directory).       The flags argument is a bit mask that can include zero or more  of  the       following flags:       AT_EMPTY_PATH              If  pathname is an empty string, operate on the file referred to              by dirfd (which may have been obtained using theopen(2)  O_PATH              flag).       AT_SYMLINK_NOFOLLOW              If  the  file  identified  by dirfd and a non-NULL pathname is a              symbolic link, then the call fails with the error ELOOP.RETURN VALUE       On success, execveat() does not return.  On error, -1 is returned,  and       errno is set appropriately.ERRORS       The same errors that occur forexecve(2) can also occur for execveat().       The following additional errors can occur for execveat():       EBADF  dirfd is not a valid file descriptor.       EINVAL Invalid flag specified in flags.       ELOOP  flags includes AT_SYMLINK_NOFOLLOW and the  file  identified  by              dirfd and a non-NULL pathname is a symbolic link.       ENOENT The program identified by dirfd and pathname requires the use of              an interpreter program (such as a script  starting  with  "#!"),              but  the  file  descriptor  dirfd  was opened with the O_CLOEXEC              flag, with the result that the program file is  inaccessible  to              the launched interpreter.  See BUGS.       ENOTDIR              pathname is relative and dirfd is a file descriptor referring to              a file other than a directory.VERSIONS       execveat() was added to Linux in kernel 3.19.  GNU C library support is       pending.CONFORMING TO       The execveat() system call is Linux-specific.NOTES       In  addition to the reasons explained inopenat(2), the execveat() sys-       tem call is also needed to allowfexecve(3) to be implemented  on  sys-       tems that do not have the /proc filesystem mounted.       When  asked to execute a script file, the argv[0] that is passed to the       script interpreter is a string of the form  /dev/fd/N  or  /dev/fd/N/P,       where N is the number of the file descriptor passed via the dirfd argu-       ment.  A string of the first form  occurs  when  AT_EMPTY_PATH  is  em-       ployed.   A  string of the second form occurs when the script is speci-       fied via both dirfd and pathname; in this case, P is the value given in       pathname.       For  the  same  reasons described infexecve(3), the natural idiom when       using execveat() is to set the close-on-exec flag on dirfd.   (But  see       BUGS.)BUGS       The  ENOENT  error described above means that it is not possible to set       the close-on-exec flag on the file descriptor given to a  call  of  the       form:           execveat(fd, "", argv, envp, AT_EMPTY_PATH);       However,  the inability to set the close-on-exec flag means that a file       descriptor referring to the script leaks through to the script  itself.       As well as wasting a file descriptor, this leakage can lead to file-de-       scriptor exhaustion in scenarios where scripts recursively  employ  ex-       ecveat().SEE ALSOexecve(2),openat(2),fexecve(3)COLOPHON       This  page  is  part of release 5.05 of the Linux man-pages project.  A       description of the project, information about reporting bugs,  and  the       latest     version     of     this    page,    can    be    found    at       https://www.kernel.org/doc/man-pages/.Linux                             2017-09-15EXECVEAT(2)