execveat - execute program relative to a directory file descriptor

       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-
       descriptor exhaustion in scenarios where scripts recursively employ execveat().

       The execveat() system call executes the program referred to by the combination of dirfd and pathname.  It
       operates in exactly the same way as execve(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 by execve(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 (like execve(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 the open(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.

       The  same errors that occur for execve(2) can also occur for execveat().  The following additional errors
       can occur for execveat():

       pathname
              is relative but dirfd is neither AT_FDCWD nor a valid file descriptor.

       EINVAL Invalid flag specified in flags.

       ELOOPflags 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.

       ENOTDIRpathname is relative and dirfd is a file descriptor referring to a file other than a directory.

       Linux 3.19, glibc 2.34.

       Standard C library (libc, -lc)

       execveat - execute program relative to a directory file descriptor

       In  addition  to  the  reasons explained in openat(2), the execveat() system call is also needed to allow
       fexecve(3) to be implemented on systems 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
       argument.  A string of the first form occurs when AT_EMPTY_PATH is employed.  A string of the second form
       occurs when the script is specified via both dirfd and pathname; in this case, P is the  value  given  in
       pathname.

       For  the  same  reasons  described  in  fexecve(3), the natural idiom when using execveat() is to set the
       close-on-exec flag on dirfd.  (But see BUGS.)

       On success, execveat() does not return.  On error, -1 is returned, and  errno  is  set  to  indicate  the
       error.

execve(2), openat(2), fexecve(3)

Linux man-pages 6.9.1                              2024-05-02                                        execveat(2)

       Linux.

#include<linux/fcntl.h>      /* Definition of AT_* constants */
       #include<unistd.h>intexecveat(intdirfd,constchar*pathname,char*const_Nullableargv[],char*const_Nullableenvp[],intflags);