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LIBEXPECT(3)									     LIBEXPECT(3)

       libexpect - programmed dialogue with interactive programs - C functions

       This  library  contains functions that allow Expect to be used as a Tcl extension or to be
       used directly from C or C++ (without Tcl).  Adding Expect as a Tcl extension is very short
       and simple, so that will be covered first.

       #include expect_tcl.h

       cc files... -lexpect5.20 -ltcl7.5 -lm

       Note: library versions may differ in the actual release.

       The  Expect_Init  function adds expect commands to the named interpreter.  It avoids over-
       writing commands that already exist, however aliases beginning with "exp_" are always cre-
       ated for expect commands.  So for example, "send" can be used as "exp_send".

       Generally, you should only call Expect commands via Tcl_Eval.  Certain auxiliary functions
       may be called directly.	They are summarized below.  They may be  useful  in  constructing
       your  own main.	Look at the file exp_main_exp.c in the Expect distribution as a prototype
       main.  Another prototype is tclAppInit.c in the Tcl source distribution.  A prototype  for
       working with Tk is in exp_main_tk.c in the Expect distribution.

       int exp_cmdlinecmds;
       int exp_interactive;
       FILE *exp_cmdfile;
       char *exp_cmdfilename;
       int exp_tcl_debugger_available;

       void exp_parse_argv(Tcl_Interp *,int argc,char **argv);
       int  exp_interpreter(Tcl_Interp *);
       void exp_interpret_cmdfile(Tcl_Interp *,FILE *);
       void exp_interpret_cmdfilename(Tcl_Interp *,char *);
       void exp_interpret_rcfiles(Tcl_Interp *,int my_rc,int sys_rc);
       char *	 exp_cook(char *s,int *len);
       void (*exp_app_exit)EXP_PROTO((Tcl_Interp *);
       void exp_exit(Tcl_Interp *,int status);
       void exp_exit_handlers(Tcl_Interp *);
       void exp_error(Tcl_Interp,char *,...);

       exp_cmdlinecmds	is 1 if Expect has been invoked with commands on the program command-line
       (using "-c" for example).  exp_interactive is 1 if Expect has been  invoked  with  the  -i
       flag  or  if  no  commands or script is being invoked.  exp_cmdfile is a stream from which
       Expect will read commands.  exp_cmdfilename is the name of a file which Expect  will  open
       and read commands from.	exp_tcl_debugger_available is 1 if the debugger has been armed.

       exp_parse_argv  reads the representation of the command line.  Based on what is found, any
       of the other variables listed here are initialized appropriately.  exp_interpreter  inter-
       actively  prompts  the  user for commands and evaluates them.  exp_interpret_cmdfile reads
       the given stream and evaluates any commands found.   exp_interpret_cmdfilename  opens  the
       named file and evaluates any commands found.  exp_interpret_rcfiles reads and evalutes the
       .rc files.  If my_rc is zero, then ~/.expectrc is skipped.  If sys_rc is  zero,	then  the
       system-wide  expectrc  file  is	skipped.  exp_cook returns a static buffer containing the
       argument reproduced with newlines replaced by  carriage-return  linefeed  sequences.   The
       primary purpose of this is to allow messages to be produced without worrying about whether
       the terminal is in raw mode or cooked mode.  If length is zero, it is computed via strlen.
       exp_error is a printf-like function that writes the result to interp->result.

       #include <expect.h>

       exp_spawnl(file, arg0 [, arg1, ..., argn] (char *)0);
       char *file;
       char *arg0, *arg1, ... *argn;

       char *file, *argv[ ];

       int fd;

       FILE *
       char *command;

       extern int exp_pid;
       extern int exp_ttyinit;
       extern int exp_ttycopy;
       extern int exp_console;
       extern char *exp_stty_init;
       extern void (*exp_close_in_child)();
       extern void (*exp_child_exec_prelude)();
       extern void exp_close_tcl_files();

       cc files... -lexpect -ltcl -lm

       exp_spawnl  and exp_spawnv fork a new process so that its stdin, stdout, and stderr can be
       written and read by the current process.  file is the name of a file to be executed.   The
       arg  pointers  are  null-terminated  strings.   Following  the style of execve(), arg0 (or
       argv[0]) is customarily a duplicate of the name of the file.

       Four interfaces are available, exp_spawnl is useful when the number of arguments is  known
       at  compile  time.  exp_spawnv is useful when the number of arguments is not known at com-
       pile time.  exp_spawnfd is useful when an open file descriptor is already available  as	a
       source.	exp_popen is explained later on.

       If the process is successfully created, a file descriptor is returned which corresponds to
       the process's stdin, stdout and stderr.	A stream may be associated with the file descrip-
       tor  by using fdopen().	(This should almost certainly be followed by setbuf() to unbuffer
       the I/O.)

       Closing the file descriptor will typically be detected by the process  as  an  EOF.   Once
       such  a	process exits, it should be waited upon (via wait) in order to free up the kernel
       process slot.  (Some systems allow you to avoid this if you ignore the SIGCHLD signal).

       exp_popen is yet another interface, styled after popen().  It takes a Bourne shell command
       line,  and  returns  a  stream that corresponds to the process's stdin, stdout and stderr.
       The actual implementation of exp_popen below demonstrates exp_spawnl.

       FILE *
       char *program;
	    FILE *fp;
	    int ec;

	    if (0 > (ec = exp_spawnl("sh","sh","-c",program,(char *)0)))
	    if (NULL == (fp = fdopen(ec,"r+")) return(0);
	    setbuf(fp,(char *)0);

       After a process is started, the variable exp_pid is set	to  the  process-id  of  the  new
       process.  The variable exp_pty_slave_name is set to the name of the slave side of the pty.

       The  spawn  functions  uses a pty to communicate with the process.  By default, the pty is
       initialized the same way as the user's tty (if possible, i.e., if the  environment  has	a
       controlling terminal.)  This initialization can be skipped by setting exp_ttycopy to 0.

       The  pty  is  further initialized to some system wide defaults if exp_ttyinit is non-zero.
       The default is generally comparable to "stty sane".

       The tty setting can be further modified by setting the variable exp_stty_init.  This vari-
       able  is interpreted in the style of stty arguments.  For example, exp_stty_init = "sane";
       repeats the default initialization.

       On some systems, it is possible to redirect console output to ptys.  If this is supported,
       you can force the next spawn to obtain the console output by setting the variable exp_con-
       sole to 1.

       Between the time a process is started and the new program  is  given  control,  the  spawn
       functions  can clean up the environment by closing file descriptors.  By default, the only
       file descriptors closed are ones internal to Expect and any marked "close-on-exec".

       If needed, you can close additional file descriptors by creating an  appropriate  function
       and  assigning  it  to exp_close_in_child.  The function will be called after the fork and
       before the exec.  (This also modifies the behavior of the spawn command in Expect.)

       If you are also using Tcl, it may be convenient to use  the  function  exp_close_tcl_files
       which  closes  all  files  between  the	default standard file descriptors and the highest
       descriptor known to Tcl.  (Expect does this.)

       The function exp_child_exec_prelude is the last function called prior to the  actual  exec
       in  the child.  You can redefine this for effects such as manipulating the uid or the sig-

       extern int exp_autoallocpty;
       extern int exp_pty[2];

       The spawn functions use a pty to communicate with the process.  By default, a pty is auto-
       matically  allocated  each  time a process is spawned.  If you want to allocate ptys your-
       self, before calling one of the spawn functions, set exp_autoallocpty to 0, exp_pty[0]  to
       the  master  pty  file  descriptor  and	exp_pty[1] to the slave pty file descriptor.  The
       expect library will not do any pty initializations (e.g., exp_stty_init will not be used).
       The  slave  pty	file descriptor will be automatically closed when the process is spawned.
       After the process is started, all further communication takes place with  the  master  pty
       file descriptor.

       exp_spawnl  and	exp_spawnv  duplicate  the shell's actions in searching for an executable
       file in a list of directories.  The directory list is obtained from the environment.

       While it is possible to	use  read()  to  read  information  from  a  process  spawned  by
       exp_spawnl or exp_spawnv, more convenient functions are provided.  They are as follows:

       int fd;
       enum exp_type type;
       char *pattern1, *pattern2, ...;
       regexp *re1, *re2, ...;
       int value1, value2, ...;

       FILE *fp;
       enum exp_type type;
       char *pattern1, *pattern2, ...;
       regexp *re1, *re2, ...;
       int value1, value2, ...;

       enum exp_type {

       struct exp_case {
       char *pattern;
       regexp *re;
       enum exp_type type;
       int value;

       int fd;
       struct exp_case *cases;

       FILE *fp;
       struct exp_case *cases;

       extern int exp_timeout;
       extern char *exp_match;
       extern char *exp_match_end;
       extern char *exp_buffer;
       extern char *exp_buffer_end;
       extern int exp_match_max;
       extern int exp_full_buffer;
       extern int exp_remove_nulls;

       The  functions  wait until the output from a process matches one of the patterns, a speci-
       fied time period has passed, or an EOF is seen.

       The first argument to each function is either a file descriptor or a  stream.   Successive
       sets  of arguments describe patterns and associated integer values to return when the pat-
       tern matches.

       The type argument is one of four values.  exp_end indicates that no more patterns  appear.
       exp_glob  indicates  that the pattern is a glob-style string pattern.  exp_exact indicates
       that the pattern is an exact string.  exp_regexp indicates that the pattern is  a  regexp-
       style  string  pattern.	 exp_compiled indicates that the pattern is a regexp-style string
       pattern, and that its compiled form is also provided.  exp_null indicates that the pattern
       is a null (for debugging purposes, a string pattern must also follow).

       If  the compiled form is not provided with the functions exp_expectl and exp_fexpectl, any
       pattern compilation done internally is thrown away after the function returns.  The  func-
       tions  exp_expectv and exp_fexpectv will automatically compile patterns and will not throw
       them away.  Instead, they must be discarded by the user, by calling free on each  pattern.
       It is only necessary to discard them, the last time the cases are used.

       Regexp  subpatterns  matched  are stored in the compiled regexp.  Assuming "re" contains a
       compiled regexp, the matched string can be found in re->startp[0].  The	match  substrings
       (according  to  the  parentheses)  in  the original pattern can be found in re->startp[1],
       re->startp[2], and so on,  up  to  re->startp[9].   The	corresponding  strings	ends  are
       re->endp[x] where x is that same index as for the string start.

       The  type  exp_null matches if a null appears in the input.  The variable exp_remove_nulls
       must be set to 0  to  prevent  nulls  from  being  automatically  stripped.   By  default,
       exp_remove_nulls is set to 1 and nulls are automatically stripped.

       exp_expectv  and  exp_fexpectv  are  useful  when  the  number of patterns is not known in
       advance.  In this case, the sets are provided in an  array.   The  end  of  the	array  is
       denoted	by  a  struct exp_case with type exp_end.  For the rest of this discussion, these
       functions will be referred to generically as expect.

       If a pattern matches, then the corresponding integer value is returned.	Values	need  not
       be  unique, however they should be positive to avoid being mistaken for EXP_EOF, EXP_TIME-
       OUT, or EXP_FULLBUFFER.	Upon  EOF  or  timeout,  the  value  EXP_EOF  or  EXP_TIMEOUT  is
       returned.   The	default  timeout  period  is 10 seconds but may be changed by setting the
       variable exp_timeout.  A value of -1 disables a timeout from  occurring.   A  value  of	0
       causes  the  expect function to return immediately (i.e., poll) after one read().  However
       it must be preceded by a function such as select, poll, or an event  manager  callback  to
       guarantee that there is data to be read.

       If  the variable exp_full_buffer is 1, then EXP_FULLBUFFER is returned if exp_buffer fills
       with no pattern having matched.

       When the expect function returns, exp_buffer points to the buffer of characters	that  was
       being  considered  for  matching.  exp_buffer_end points to one past the last character in
       exp_buffer.  If a match occurred, exp_match points into exp_buffer where the match  began.
       exp_match_end points to one character past where the match ended.

       Each  time new input arrives, it is compared to each pattern in the order they are listed.
       Thus, you may test for absence of a match by making the last pattern something  guaranteed
       to  appear,  such as a prompt.  In situations where there is no prompt, you must check for
       EXP_TIMEOUT (just like you would if you were interacting manually).  More  philosophy  and
       strategies  on  specifying expect patterns can be found in the documentation on the expect
       program itself.	See SEE ALSO below.

       Patterns are the usual C-shell-style regular  expressions.   For  example,  the	following
       fragment looks for a successful login, such as from a telnet dialogue.

	    switch (exp_expectl(
		 exp_glob,"invalid password",ABORT,
		 exp_end)) {
	    case CONN:	   /* logged in successfully */
	    case BUSY:	   /* couldn't log in at the moment */
	    case EXP_TIMEOUT:
	    case ABORT:    /* can't log in at any moment! */
	    default: /* problem with expect */

       Asterisks  (as  in the example above) are a useful shorthand for omitting line-termination
       characters and other detail.  Patterns must match the entire output of the current process
       (since the previous read on the descriptor or stream).  More than 2000 bytes of output can
       force earlier bytes to be "forgotten".  This  may  be  changed  by  setting  the  variable
       exp_match_max.  Note that excessively large values can slow down the pattern matcher.

       extern int exp_disconnected;
       int exp_disconnect();

       It  is possible to move a process into the background after it has begun running.  A typi-
       cal use for this is to read passwords and then go into  the  background	to  sleep  before
       using the passwords to do real work.

       To  move  a  process into the background, fork, call exp_disconnect() in the child process
       and exit() in the parent process.  This disassociates your process  from  the  controlling
       terminal.   If you wish to move a process into the background in a different way, you must
       set the variable exp_disconnected to 1.	This allows processes spawned after this point to
       be started correctly.

       By  default,  the expect functions block inside of a read on a single file descriptor.  If
       you want to wait on patterns from multiple file descriptors, use select, poll, or an event
       manager.  They will tell you what file descriptor is ready to read.

       When  a	file  descriptor is ready to read, you can use the expect functions to do one and
       only read by setting timeout to 0.

       int fd;
       int enable;

       Pty trapping is normally done automatically by the expect functions.  However, if you want
       to issue an ioctl, for example, directly on the slave device, you should temporary disable

       Pty trapping can be controlled with exp_slave_control.  The first  argument  is	the  file
       descriptor  corresponding  to the spawned process.  The second argument is a 0 if trapping
       is to be disabled and 1 if it is to be enabled.

       All functions indicate errors by returning -1 and setting errno.

       Errors that occur after the spawn functions fork (e.g., attempting to spawn a non-existent
       program) are written to the process's stderr, and will be read by the first expect.

       extern int exp_reading;
       extern jmp_buf exp_readenv;

       expect uses alarm() to timeout, thus if you generate alarms during expect, it will timeout

       Internally, expect calls read() which can be interrupted by signals.  If you define signal
       handlers,  you  can  choose  to	restart  or  abort expect's internal read.  The variable,
       exp_reading,  is  true  if  (and  only	if)   expect's	 read	has   been   interrupted.
       longjmp(exp_readenv,EXP_ABORT) will abort the read.  longjmp(exp_readenv,EXP_RESTART) will
       restart the read.

       extern int exp_loguser;
       extern int exp_logfile_all
       extern FILE *exp_logfile;

       If exp_loguser is nonzero, expect sends any output from the  spawned  process  to  stdout.
       Since  interactive programs typically echo their input, this usually suffices to show both
       sides of the conversation.  If exp_logfile is also nonzero, this same output is written to
       the stream defined by exp_logfile.  If exp_logfile_all is non-zero, exp_logfile is written
       regardless of the value of exp_loguser.

       While I consider the library to be easy to use, I think that the standalone expect program
       is much, much, easier to use than working with the C compiler and its usual edit, compile,
       debug cycle.  Unlike typical C programs, most of the debugging isn't getting  the  C  com-
       piler  to accept your programs - rather, it is getting the dialogue correct.  Also, trans-
       lating scripts from expect to C is usually not  necessary.   For  example,  the	speed  of
       interactive  dialogues is virtually never an issue.  So please try the standalone 'expect'
       program first.  I suspect it is a more appropriate  solution  for  most	people	than  the

       Nonetheless, if you feel compelled to debug in C, here are some tools to help you.

       extern int exp_is_debugging;
       extern FILE *exp_debugfile;

       While  expect dialogues seem very intuitive, trying to codify them in a program can reveal
       many surprises in a program's interface.  Therefore a variety of debugging aids are avail-
       able.  They are controlled by the above variables, all 0 by default.

       Debugging  information  internal to expect is sent to stderr when exp_is_debugging is non-
       zero.  The debugging information includes every character received, and every attempt made
       to  match  the  current input against the patterns.  In addition, non-printable characters
       are translated to a printable form.  For example, a control-C appears as a caret  followed
       by a C.	If exp_logfile is non-zero, this information is also written to that stream.

       If  exp_debugfile  is  non-zero,  all  normal and debugging information is written to that
       stream, regardless of the value of exp_is_debugging.

       The stream versions of the expect functions are much slower than the file descriptor  ver-
       sions  because  there  is  no  way to portably read an unknown number of bytes without the
       potential of timing out.  Thus, characters are read one at  a  time.   You  are	therefore
       strongly  encouraged  to  use  the file descriptor versions of expect (although, automated
       versions of interactive programs don't usually demand high speed anyway).

       You can actually get the best of both worlds, writing with the usual stream functions  and
       reading with the file descriptor versions of expect as long as you don't attempt to inter-
       mix other stream input functions (e.g., fgetc).	To do this, pass  fileno(stream)  as  the
       file  descriptor  each  time.  Fortunately, there is little reason to use anything but the
       expect functions when reading from interactive programs.

       There is no matching exp_pclose to exp_popen (unlike popen and pclose).	It only takes two
       functions  to close down a connection (fclose() followed by waiting on the pid), but it is
       not uncommon to separate these two actions by large time intervals, so the function  seems
       of little value.

       If  you	are  running  on a Cray running Unicos (all I know for sure from experience), you
       must run your compiled program as root or setuid.  The  problem	is  that  the  Cray  only
       allows  root  processes to open ptys.  You should observe as much precautions as possible:
       If you don't need permissions, setuid(0) only immediately before calling one of the  spawn
       functions and immediately set it back afterwards.

       Normally,  spawn  takes	little time to execute.  If you notice spawn taking a significant
       amount of time, it is probably encountering ptys that are wedged.  A number of  tests  are
       run  on	ptys  to  avoid  entanglements with errant processes.  (These take 10 seconds per
       wedged pty.)  Running expect with the -d option will show if expect is  encountering  many
       ptys  in  odd  states.  If you cannot kill the processes to which these ptys are attached,
       your only recourse may be to reboot.

       The exp_fexpect functions don't work at all under HP-UX - it appears to be a bug in  getc.
       Follow the advice (above) about using the exp_expect functions (which doesn't need to call
       getc).  If you fix the problem (before I do - please check  the	latest	release)  let  me

       An  alternative	to this library is the expect program.	expect interprets scripts written
       in a high-level language which direct the dialogue.  In addition, the user can  take  con-
       trol  and interact directly when desired.  If it is not absolutely necessary to write your
       own C program, it is much easier to use expect to perform the entire interaction.   It  is
       described further in the following references:

       "expect:  Curing  Those Uncontrollable Fits of Interactivity" by Don Libes, Proceedings of
       the Summer 1990 USENIX Conference, Anaheim, California, June 11-15, 1990.

       "Using expect to Automate System Administration Tasks" by Don Libes,  Proceedings  of  the
       1990  USENIX  Large Installation Systems Administration Conference, Colorado Springs, Col-
       orado, October 17-19, 1990.

       expect(1), alarm(3),  read(2),  write(2),  fdopen(3),  execve(2),  execvp(3),  longjmp(3),

       There  are  several examples C programs in the test directory of expect's source distribu-
       tion which use the expect library.

       Don Libes, libes@nist.gov, National Institute of Standards and Technology

       Thanks to John Ousterhout (UCBerkeley) for supplying the pattern matcher.

       Design and implementation of the expect library was paid for by the U.S. government and is
       therefore  in  the  public  domain.  However the author and NIST would like credit if this
       program and documentation or portions of them are used.

					 12 December 1991			     LIBEXPECT(3)
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