| EXEC(3) | Library Functions Manual | EXEC(3) | 
execl, execlp,
  execlpe, execle,
  exect, execv,
  execvp, execvpe —
#include <unistd.h>
extern char **environ;
int
  
  execl(const
    char *path, const char
    *arg, ...);
int
  
  execlp(const
    char *file, const char
    *arg, ...);
int
  
  execlpe(const
    char *file, const char
    *arg, ...,
    char *const envp[]);
int
  
  execle(const
    char *path, const char
    *arg, ...,
    char *const envp[]);
int
  
  exect(const
    char *path, char *const
    argv[], char *const
    envp[]);
int
  
  execv(const
    char *path, char *const
    argv[]);
int
  
  execvp(const
    char *file, char *const
    argv[]);
int
  
  execvpe(const
    char *file, char *const
    argv[], char *const
    envp[]);
exec() family of functions replaces the current
  process image with a new process image. The functions described in this manual
  page are front-ends for the function
  execve(2). (See the manual page
  for execve(2) for detailed
  information about the replacement of the current process. The
  script(7) manual page provides
  detailed information about the execution of interpreter scripts.)
The initial argument for these functions is the pathname of a file which is to be executed.
The const char *arg and subsequent ellipses
    in the execl(), execlp(),
    execlpe(), and execle()
    functions can be thought of as arg0,
    arg1, ..., argn. Together they describe
    a list of one or more pointers to NUL-terminated strings that represent the
    argument list available to the executed program. The first argument, by
    convention, should point to the file name associated with the file being
    executed. The list of arguments must be terminated by a
    NULL pointer.
The exect(),
    execv(), execvp(), and
    execvpe() functions provide an array of pointers to
    NUL-terminated strings that represent the argument list available to the new
    program. The first argument, by convention, should point to the file name
    associated with the file being executed. The array of pointers
    must be terminated by a NULL
    pointer.
The execle(),
    execlpe(), exect(), and
    execvpe() functions also specify the environment of
    the executed process by following the NULL pointer
    that terminates the list of arguments in the parameter list or the pointer
    to the argv array with an additional parameter. This additional parameter is
    an array of pointers to NUL-terminated strings and must be
    terminated by a NULL pointer. The other functions
    take the environment for the new process image from the external variable
    environ in the current process.
Some of these functions have special semantics.
The functions execlp(),
    execlpe(), execvp(), and
    execvpe() will duplicate the actions of the shell in
    searching for an executable file if the specified file name does not contain
    a slash “/” character. The search path
    is the path specified in the environment by the PATH
    variable. If this variable isn't specified,
    _PATH_DEFPATH from
    <paths.h> is used instead,
    its value being:
    /usr/bin:/bin:/usr/pkg/bin:/usr/local/bin. In
    addition, certain errors are treated specially.
If permission is denied for a file (the attempted
    execve(2) returned
    EACCES), these functions will continue searching the
    rest of the search path. If no other file is found, however, they will
    return with the global variable errno set to
    EACCES.
If the header of a file isn't recognized (the attempted
    execve(2) returned
    ENOEXEC), these functions will execute the shell
    with the path of the file as its first argument. (If this attempt fails, no
    further searching is done.)
If the file is currently busy (the attempted
    execve(2) returned
    ETXTBUSY), these functions will sleep for several
    seconds, periodically re-attempting to execute the file.
The function exect() executes a file with
    the program tracing facilities enabled (see
    ptrace(2)).
exec() functions returns, an error will
  have occurred. The return value is -1, and the global variable
  errno will be set to indicate the error.
execlp()
  execlpe(), execvp(), and
  execvpe() functions was
  “:/bin:/usr/bin”. This was changed to
  improve security and behaviour.
The behavior of execlp(),
    execlpe(), execvp(), and
    execvpe() when errors occur while attempting to
    execute the file is historic practice, but has not traditionally been
    documented and is not specified by the POSIX standard.
Traditionally, the functions execlp(),
    execlpe(), execvp(), and
    execvpe() ignored all errors except for the ones
    described above and ENOMEM and
    E2BIG, upon which they returned. They now return if
    any error other than the ones described above occurs.
execl(), execle(),
  execlp(), execlpe(),
  execvp(), and execvpe() may
  fail and set errno for any of the errors specified for
  the library functions execve(2)
  and malloc(3).
exect() and
    execv() may fail and set errno
    for any of the errors specified for the library function
    execve(2).
execl(), execv(),
  execle(), execlp(), and
  execvp() conform to IEEE Std
  1003.1-1990 (“POSIX.1”).
exec() function appeared in
  Version 1 AT&T UNIX. The
  execlpe() function appeared first in QNX and the
  execvpe() function exists on both
  NetBSD and QNX.
| September 1, 2019 | NetBSD 10.0 |