man2/execveat.2

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  25 .TH EXECVEAT 2 2014-04-02 "Linux" "Linux Programmer's Manual"
  26 .SH NAME
  27 execveat \- execute program relative to a directory file descriptor
  28 .SH SYNOPSIS
  29 .B #include <unistd.h>
  30 .sp
  31 .BI "int execveat(int " fd ", const char *" pathname ","
  32 .br
  33 .BI "             char *const " argv "[],  char *const " envp "[],"
  34 .br
  35 .BI "             int " flags);
  36 .SH DESCRIPTION
  37 The
  38 .BR execveat ()
  39 system call executes the program pointed to by the combination of \fIfd\fP and \fIpathname\fP.
  40 The
  41 .BR execveat ()
  42 system call operates in exactly the same way as
  43 .BR execve (2),
  44 except for the differences described in this manual page.
  45
  46 If the pathname given in
  47 .I pathname
  48 is relative, then it is interpreted relative to the directory
  49 referred to by the file descriptor
  50 .I fd
  51 (rather than relative to the current working directory of
  52 the calling process, as is done by
  53 .BR execve (2)
  54 for a relative pathname).
  55
  56 If
  57 .I pathname
  58 is relative and
  59 .I fd
  60 is the special value
  61 .BR AT_FDCWD ,
  62 then
  63 .I pathname
  64 is interpreted relative to the current working
  65 directory of the calling process (like
  66 .BR execve (2)).
  67
  68 If
  69 .I pathname
  70 is absolute, then
  71 .I fd
  72 is ignored.
  73
  74 If
  75 .I pathname
  76 is an empty string and the
  77 .BR AT_EMPTY_PATH
  78 flag is specified, then the file descriptor
  79 .I fd
  80 specifies the file to be executed.
  81
  82 .I flags
  83 can either be 0, or include the following flags:
  84 .TP
  85 .BR AT_EMPTY_PATH
  86 If
  87 .I pathname
  88 is an empty string, operate on the file referred to by
  89 .IR fd
  90 (which may have been obtained using the
  91 .BR open (2)
  92 .B O_PATH
  93 flag).
  94 .TP
  95 .B AT_SYMLINK_NOFOLLOW
  96 If the file identified by
  97 .I fd
  98 and a non-NULL
  99 .I pathname
 100 is a symbolic link, then the call fails with the error
 101 .BR EINVAL .
 102 .SH "RETURN VALUE"
 103 On success,
 104 .BR execveat ()
 105 does not return. On error \-1 is returned, and
 106 .I errno
 107 is set appropriately.
 108 .SH ERRORS
 109 The same errors that occur for
 110 .BR execve (2)
 111 can also occur for
 112 .BR execveat ().
 113 The following additional errors can occur for
 114 .BR execveat ():
 115 .TP
 116 .B EBADF
 117 .I fd
 118 is not a valid file descriptor.
 119 .TP
 120 .B ENOENT
 121 The program identified by \fIfd\fP and \fIpathname\fP requires the
 122 use of an interpreter program (such as a script starting with
 123 "#!") but the file descriptor
 124 .I fd
 125 was opened with the
 126 .B O_CLOEXEC
 127 flag and so the program file is inaccessible to the launched interpreter.
 128 .TP
 129 .B EINVAL
 130 Invalid flag specified in
 131 .IR flags .
 132 .TP
 133 .B ENOTDIR
 134 .I pathname
 135 is relative and
 136 .I fd
 137 is a file descriptor referring to a file other than a directory.
 138 .SH VERSIONS
 139 .BR execveat ()
 140 was added to Linux in kernel 3.???.
 141 .SH NOTES
 142 In addition to the reasons explained in
 143 .BR openat (2),
 144 the
 145 .BR execveat ()
 146 system call is also needed to allow
 147 .BR fexecve (3)
 148 to be implemented on systems that do not have the
 149 .I /proc
 150 filesystem mounted.
 151 .SH SEE ALSO
 152 .BR execve (2),
 153 .BR fexecve (3)