Octave Systems Tools
Controlling Subprocesses
========================
Octave includes some high-level commands like `system' and `popen'
for starting subprocesses. If you want to run another program to
perform some task and then look at its output, you will probably want
to use these functions.
Octave also provides several very low-level Unix-like functions which
can also be used for starting subprocesses, but you should probably only
use them if you can't find any way to do what you need with the
higher-level functions.
- Built-in Function: system (STRING, RETURN_OUTPUT, TYPE)
Execute a shell command specified by STRING. The second argument
is optional. If TYPE is `"async"', the process is started in the
background and the process id of the child process is returned
immediately. Otherwise, the process is started, and Octave waits
until it exits. If TYPE argument is omitted, a value of `"sync"'
is assumed.
If two input arguments are given (the actual value of
RETURN_OUTPUT is irrelevant) and the subprocess is started
synchronously, or if SYSTEM is called with one input argument and
one or more output arguments, the output from the command is
returned. Otherwise, if the subprocess is executed synchronously,
it's output is sent to the standard output. To send the output of
a command executed with SYSTEM through the pager, use a command
like
disp (system (cmd, 1));
or
printf ("%s
", system (cmd, 1));
The `system' function can return two values. The first is any
output from the command that was written to the standard output
stream, and the second is the output status of the command. For
example,
[output, status] = system ("echo foo; exit 2");
will set the variable `output' to the string `foo', and the
variable `status' to the integer `2'.
- Built-in Function: fid = popen (COMMAND, MODE)
Start a process and create a pipe. The name of the command to run
is given by COMMAND. The file identifier corresponding to the
input or output stream of the process is returned in FID. The
argument MODE may be
`"r"'
The pipe will be connected to the standard output of the
process, and open for reading.
`"w"'
The pipe will be connected to the standard input of the
process, and open for writing.
For example,
fid = popen ("ls -ltr / | tail -3", "r");
while (isstr (s = fgets (fid)))
fputs (stdout, s);
endwhile
-| drwxr-xr-x 33 root root 3072 Feb 15 13:28 etc
-| drwxr-xr-x 3 root root 1024 Feb 15 13:28 lib
-| drwxrwxrwt 15 root root 2048 Feb 17 14:53 tmp
- Built-in Function: pclose (FID)
Close a file identifier that was opened by `popen'. You may also
use `fclose' for the same purpose.
- Function File: [IN, OUT, PID] = popen2 (COMMAND, ARGS)
Start a subprocess with two-way communication. The name of the
process is given by COMMAND, and ARGS is an array of strings
containing options for the command. The file identifiers for the
input and output streams of the subprocess are returned in IN and
OUT. If execution of the command is successful, PID contains the
process ID of the subprocess. Otherwise, PID is -1.
For example,
[in, out, pid] = popen2 ("sort", "-nr");
fputs (in, "these\nare\nsome\nstrings\n");
fclose (in);
while (isstr (s = fgets (out)))
fputs (stdout, s);
endwhile
fclose (out);
-| are
-| some
-| strings
-| these
- Built-in Variable: EXEC_PATH
The variable `EXEC_PATH' is a colon separated list of directories
to search when executing subprograms. Its initial value is taken
from the environment variable `OCTAVE_EXEC_PATH' (if it exists) or
`PATH', but that value can be overridden by the command line
argument `--exec-path PATH', or by setting the value of
`EXEC_PATH' in a startup script. If the value of `EXEC_PATH'
begins (ends) with a colon, the directories
OCTAVE-HOME/libexec/octave/site/exec/ARCH
OCTAVE-HOME/libexec/octave/VERSION/exec/ARCH
are prepended (appended) to `EXEC_PATH', where OCTAVE-HOME is the
top-level directory where all of Octave is installed (the default
value is `/usr/local'). If you don't specify a value for
`EXEC_PATH' explicitly, these special directories are prepended to
your shell path.
In most cases, the following functions simply decode their arguments
and make the corresponding Unix system calls. For a complete example
of how they can be used, look at the definition of the function
`popen2'.
- Built-in Function: [PID, MSG] = fork ()
Create a copy of the current process.
Fork can return one of the following values:
> 0
You are in the parent process. The value returned from
`fork' is the process id of the child process. You should
probably arrange to wait for any child processes to exit.
0
You are in the child process. You can call `exec' to start
another process. If that fails, you should probably call
`exit'.
< 0
The call to `fork' failed for some reason. You must take
evasive action. A system dependent error message will be
waiting in MSG.
- Built-in Function: [ERR, MSG] = exec (FILE, ARGS)
Replace current process with a new process. Calling `exec' without
first calling `fork' will terminate your current Octave process and
replace it with the program named by FILE. For example,
exec ("ls" "-l")
will run `ls' and return you to your shell prompt.
If successful, `exec' does not return. If `exec' does return, ERR
will be nonzero, and MSG will contain a system-dependent error
message.
- Built-in Function: [FILE_IDS, ERR, MSG] = pipe ()
Create a pipe and return the vector FILE_IDS, which corresponding
to the reading and writing ends of the pipe.
If successful, ERR is 0 and MSG is an empty string. Otherwise,
ERR is nonzero and MSG contains a system-dependent error message.
- Built-in Function: [FID, MSG] = dup2 (OLD, NEW)
Duplicate a file descriptor.
If successful, FID is greater than zero and contains the new file
ID. Otherwise, FID is negative and MSG contains a
system-dependent error message.
- Built-in Function: [PID, MSG] = waitpid (PID, OPTIONS)
Wait for process PID to terminate. The PID argument can be:
-1
Wait for any child process.
0
Wait for any child process whose process group ID is equal to
that of the Octave interpreter process.
> 0
Wait for termination of the child process with ID PID.
The OPTIONS argument can be:
0
Wait until signal is received or a child process exits (this
is the default if the OPTIONS argument is missing).
1
Do not hang if status is not immediately available.
2
Report the status of any child processes that are stopped,
and whose status has not yet been reported since they stopped.
3
Implies both 1 and 2.
If the returned value of PID is greater than 0, it is the process
ID of the child process that exited. If an error occurs, PID will
be less than zero and MSG will contain a system-dependent error
message.
- Built-in Function: [ERR, MSG] = fcntl (FID, REQUEST, ARG)
Change the properties of the open file FID. The following values
may be passed as REQUEST:
`F_DUPFD'
Return a duplicate file descriptor.
`F_GETFD'
Return the file descriptor flags for FID.
`F_SETFD'
Set the file descriptor flags for FID.
`F_GETFL'
Return the file status flags for FID. The following codes
may be returned (some of the flags may be undefined on some
systems).
`O_RDONLY'
Open for reading only.
`O_WRONLY'
Open for writing only.
`O_RDWR'
Open for reading and writing.
`O_APPEND'
Append on each write.
`O_NONBLOCK'
Nonblocking mode.
`O_SYNC'
Wait for writes to complete.
`O_ASYNC'
Asynchronous I/O.
`F_SETFL'
Set the file status flags for FID to the value specified by
ARG. The only flags that can be changed are `O_APPEND' and
`O_NONBLOCK'.
If successful, ERR is 0 and MSG is an empty string. Otherwise,
ERR is nonzero and MSG contains a system-dependent error message.
Process, Group, and User IDs
============================
- Built-in Function: pgid = getpgrp ()
Return the process group id of the current process.
- Built-in Function: pid = getpid ()
Return the process id of the current process.
- Built-in Function: pid = getppid ()
Return the process id of the parent process.
- Built-in Function: euid = geteuid ()
Return the effective user id of the current process.
- Built-in Function: uid = getuid ()
Return the real user id of the current process.
- Built-in Function: egid = getegid ()
Return the effective group id of the current process.
- Built-in Function: gid = getgid ()
Return the real group id of the current process.
Environment Variables
=====================
- Built-in Function: getenv (VAR)
Return the value of the environment variable VAR. For example,
getenv ("PATH")
returns a string containing the value of your path.
- Built-in Function: putenv (VAR, VALUE)
Set the value of the environment variable VAR to VALUE.
Current Working Directory
=========================
- Command: cd dir
- Command: chdir dir
Change the current working directory to DIR. If DIR is omitted,
the current directory is changed to the users home directory. For
example,
cd ~/octave
Changes the current working directory to `~/octave'. If the
directory does not exist, an error message is printed and the
working directory is not changed.
- Command: ls options
- Command: dir options
List directory contents. For example,
ls -l
-| total 12
-| -rw-r--r-- 1 jwe users 4488 Aug 19 04:02 foo.m
-| -rw-r--r-- 1 jwe users 1315 Aug 17 23:14 bar.m
The `dir' and `ls' commands are implemented by calling your
system's directory listing command, so the available options may
vary from system to system.
- Built-in Function: pwd ()
Return the current working directory.
Password Database Functions
===========================
Octave's password database functions return information in a
structure with the following fields.
`name'
The user name.
`passwd'
The encrypted password, if available.
`uid'
The numeric user id.
`gid'
The numeric group id.
`gecos'
The GECOS field.
`dir'
The home directory.
`shell'
The initial shell.
In the descriptions of the following functions, this data structure
is referred to as a PW_STRUCT.
- Loadable Function: PW_STRUCT = getpwent ()
Return a structure containing an entry from the password database,
opening it if necessary. Once the end of the data has been reached,
`getpwent' returns 0.
- Loadable Function: PW_STRUCT = getpwuid (UID).
Return a structure containing the first entry from the password
database with the user ID UID. If the user ID does not exist in
the database, `getpwuid' returns 0.
- Loadable Function: PW_STRUCT = getpwnam (NAME)
Return a structure containing the first entry from the password
database with the user name NAME. If the user name does not exist
in the database, `getpwname' returns 0.
- Loadable Function: setpwent ()
Return the internal pointer to the beginning of the password
database.
- Loadable Function: endpwent ()
Close the password database.
Group Database Functions
========================
Octave's group database functions return information in a structure
with the following fields.
`name'
The user name.
`passwd'
The encrypted password, if available.
`gid'
The numeric group id.
`mem'
The members of the group.
In the descriptions of the following functions, this data structure
is referred to as a GRP_STRUCT.
- Loadable Function: GRP_STRUCT = getgrent ()
Return an entry from the group database, opening it if necessary.
Once the end of the data has been reached, `getgrent' returns 0.
- Loadable Function: GRP_STRUCT = getgrgid (GID).
Return the first entry from the group database with the group ID
GID. If the group ID does not exist in the database, `getgrgid'
returns 0.
- Loadable Function: GRP_STRUCT = getgrnam (NAME)
Return the first entry from the group database with the group name
NAME. If the group name does not exist in the database,
`getgrname' returns 0.
- Loadable Function: setgrent ()
Return the internal pointer to the beginning of the group database.
- Loadable Function: endgrent ()
Close the group database.
System Information
==================
- Built-in Function: computer ()
Print or return a string of the form CPU-VENDOR-OS that identifies
the kind of computer Octave is running on. If invoked with an
output argument, the value is returned instead of printed. For
example,
computer ()
-| i586-pc-linux-gnu
x = computer ()
=> x = "i586-pc-linux-gnu"
- Built-in Function: isieee ()
Return 1 if your computer claims to conform to the IEEE standard
for floating point calculations.
- Built-in Variable: OCTAVE_VERSION
The version number of Octave, as a string.
- Built-in Function: octave_config_info (OPTION)
Return a structure containing configuration and installation
information for Octave.
if OPTION is a string, return the configuration information for the
specified option.
- Loadable Function: getrusage ()
Return a structure containing a number of statistics about the
current Octave process. Not all fields are available on all
systems. If it is not possible to get CPU time statistics, the
CPU time slots are set to zero. Other missing data are replaced
by NaN. Here is a list of all the possible fields that can be
present in the structure returned by `getrusage':
`idrss'
Unshared data size.
`inblock'
Number of block input operations.
`isrss'
Unshared stack size.
`ixrss'
Shared memory size.
`majflt'
Number of major page faults.
`maxrss'
Maximum data size.
`minflt'
Number of minor page faults.
`msgrcv'
Number of messages received.
`msgsnd'
Number of messages sent.
`nivcsw'
Number of involuntary context switches.
`nsignals'
Number of signals received.
`nswap'
Number of swaps.
`nvcsw'
Number of voluntary context switches.
`oublock'
Number of block output operations.
`stime'
A structure containing the system CPU time used. The
structure has the elements `sec' (seconds) `usec'
(microseconds).
`utime'
A structure containing the user CPU time used. The structure
has the elements `sec' (seconds) `usec' (microseconds).
Tips and Standards
******************
This chapter describes no additional features of Octave. Instead it
gives advice on making effective use of the features described in the
previous chapters.
* Menu:
* Style Tips:: Writing clean and robust programs.
* Coding Tips:: Making code run faster.
* Documentation Tips:: Writing readable documentation strings.
* Comment Tips:: Conventions for writing comments.
* Function Headers:: Standard headers for functions.
Writing Clean Octave Programs
=============================
Here are some tips for avoiding common errors in writing Octave code
intended for widespread use:
* Since all global variables share the same name space, and all
functions share another name space, you should choose a short word
to distinguish your program from other Octave programs. Then take
care to begin the names of all global variables, constants, and
functions with the chosen prefix. This helps avoid name conflicts.
If you write a function that you think ought to be added to Octave
under a certain name, such as `fiddle_matrix', don't call it by
that name in your program. Call it `mylib_fiddle_matrix' in your
program, and send mail to
suggesting that it be added to Octave. If and when it is, the
name can be changed easily enough.
If one prefix is insufficient, your package may use two or three
alternative common prefixes, so long as they make sense.
Separate the prefix from the rest of the symbol name with an
underscore `_'. This will be consistent with Octave itself and
with most Octave programs.
* When you encounter an error condition, call the function `error'
(or `usage'). The `error' and `usage' functions do not return.
*Note Errors::.
* Please put a copyright notice on the file if you give copies to
anyone. Use the same lines that appear at the top of the function
files distributed with Octave. If you have not signed papers to
assign the copyright to anyone else, then place your name in the
copyright notice.
Tips for Making Code Run Faster.
================================
Here are some ways of improving the execution speed of Octave
programs.
* Avoid looping wherever possible.
* Use iteration rather than recursion whenever possible. Function
calls are slow in Octave.
* Avoid resizing matrices unnecessarily. When building a single
result matrix from a series of calculations, set the size of the
result matrix first, then insert values into it. Write
result = zeros (big_n, big_m)
for i = over:and_over
r1 = ...
r2 = ...
result (r1, r2) = new_value ();
endfor
instead of
result = [];
for i = ever:and_ever
result = [ result, new_value() ];
endfor
* Avoid calling `eval' or `feval' whenever possible, because they
require Octave to parse input or look up the name of a function in
the symbol table.
If you are using `eval' as an exception handling mechanism and not
because you need to execute some arbitrary text, use the `try'
statement instead. *Note The try Statement::.
* If you are calling lots of functions but none of them will need to
change during your run, set the variable
`ignore_function_time_stamp' to `"all"' so that Octave doesn't
waste a lot of time checking to see if you have updated your
function files.
Tips for Documentation Strings
==============================
Here are some tips for the writing of documentation strings.
* Every command, function, or variable intended for users to know
about should have a documentation string.
* An internal variable or subroutine of an Octave program might as
well have a documentation string.
* The first line of the documentation string should consist of one
or two complete sentences that stand on their own as a summary.
The documentation string can have additional lines that expand on
the details of how to use the function or variable. The
additional lines should also be made up of complete sentences.
* For consistency, phrase the verb in the first sentence of a
documentation string as an infinitive with "to" omitted. For
instance, use "Return the frob of A and B." in preference to
"Returns the frob of A and B." Usually it looks good to do
likewise for the rest of the first paragraph. Subsequent
paragraphs usually look better if they have proper subjects.
* Write documentation strings in the active voice, not the passive,
and in the present tense, not the future. For instance, use
"Return a list containing A and B." instead of "A list containing
A and B will be returned."
* Avoid using the word "cause" (or its equivalents) unnecessarily.
Instead of, "Cause Octave to display text in boldface," write just
"Display text in boldface."
* Do not start or end a documentation string with whitespace.
* Format the documentation string so that it fits in an Emacs window
on an 80-column screen. It is a good idea for most lines to be no
wider than 60 characters.
However, rather than simply filling the entire documentation
string, you can make it much more readable by choosing line breaks
with care. Use blank lines between topics if the documentation
string is long.
* *Do not* indent subsequent lines of a documentation string so that
the text is lined up in the source code with the text of the first
line. This looks nice in the source code, but looks bizarre when
users view the documentation. Remember that the indentation
before the starting double-quote is not part of the string!
* The documentation string for a variable that is a yes-or-no flag
should start with words such as "Nonzero means...", to make it
clear that all nonzero values are equivalent and indicate
explicitly what zero and nonzero mean.
* When a function's documentation string mentions the value of an
argument of the function, use the argument name in capital letters
as if it were a name for that value. Thus, the documentation
string of the operator `/' refers to its second argument as
`DIVISOR', because the actual argument name is `divisor'.
Also use all caps for meta-syntactic variables, such as when you
show the decomposition of a list or vector into subunits, some of
which may vary.
Tips on Writing Comments
========================
Here are the conventions to follow when writing comments.
`#'
Comments that start with a single sharp-sign, `#', should all be
aligned to the same column on the right of the source code. Such
comments usually explain how the code on the same line does its
job. In the Emacs mode for Octave, the `M-;'
(`indent-for-comment') command automatically inserts such a `#' in
the right place, or aligns such a comment if it is already present.
`##'
Comments that start with two semicolons, `##', should be aligned to
the same level of indentation as the code. Such comments usually
describe the purpose of the following lines or the state of the
program at that point.
The indentation commands of the Octave mode in Emacs, such as `M-;'
(`indent-for-comment') and `TAB' (`octave-indent-line') automatically
indent comments according to these conventions, depending on the number
of semicolons. *Note Manipulating Comments: (emacs)Comments.
Conventional Headers for Octave Functions
=========================================
Octave has conventions for using special comments in function files
to give information such as who wrote them. This section explains these
conventions.
The top of the file should contain a copyright notice, followed by a
block of comments that can be used as the help text for the function.
Here is an example:
## Copyright (C) 1996, 1997 John W. Eaton
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public
## License as published by the Free Software Foundation;
## either version 2, or (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied
## warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
## PURPOSE. See the GNU General Public License for more
## details.
##
## You should have received a copy of the GNU General Public
## License along with Octave; see the file COPYING. If not,
## write to the Free Software Foundation, 59 Temple Place -
## Suite 330, Boston, MA 02111-1307, USA.
## usage: [IN, OUT, PID] = popen2 (COMMAND, ARGS)
##
## Start a subprocess with two-way communication. COMMAND
## specifies the name of the command to start. ARGS is an
## array of strings containing options for COMMAND. IN and
## OUT are the file ids of the input and streams for the
## subprocess, and PID is the process id of the subprocess,
## or -1 if COMMAND could not be executed.
##
## Example:
##
## [in, out, pid] = popen2 ("sort", "-nr");
## fputs (in, "these\nare\nsome\nstrings\n");
## fclose (in);
## while (isstr (s = fgets (out)))
## fputs (stdout, s);
## endwhile
## fclose (out);
Octave uses the first block of comments in a function file that do
not appear to be a copyright notice as the help text for the file. For
Octave to recognize the first comment block as a copyright notice, it
must match the regular expression
^ Copyright (C).*\n\n This file is part of Octave.
or
^ Copyright (C).*\n\n This program is free softwar
(after stripping the leading comment characters). This is a fairly
strict requirement, and may be relaxed somewhat in the future.
After the copyright notice and help text come several "header
comment" lines, each beginning with `## HEADER-NAME:'. For example,
## Author: jwe
## Keywords: subprocesses input-output
## Maintainer: jwe
Here is a table of the conventional possibilities for HEADER-NAME:
`Author'
This line states the name and net address of at least the principal
author of the library.
## Author: John W. Eaton
`Maintainer'
This line should contain a single name/address as in the Author
line, or an address only, or the string `jwe'. If there is no
maintainer line, the person(s) in the Author field are presumed to
be the maintainers. The example above is mildly bogus because the
maintainer line is redundant.
The idea behind the `Author' and `Maintainer' lines is to make
possible a function to "send mail to the maintainer" without
having to mine the name out by hand.
Be sure to surround the network address with `<...>' if you
include the person's full name as well as the network address.
`Created'
This optional line gives the original creation date of the file.
For historical interest only.
`Version'
If you wish to record version numbers for the individual Octave
program, put them in this line.
`Adapted-By'
In this header line, place the name of the person who adapted the
library for installation (to make it fit the style conventions, for
example).
`Keywords'
This line lists keywords. Eventually, it will be used by an
apropos command to allow people will find your package when
they're looking for things by topic area. To separate the
keywords, you can use spaces, commas, or both.
Just about every Octave function ought to have the `Author' and
`Keywords' header comment lines. Use the others if they are
appropriate. You can also put in header lines with other header
names--they have no standard meanings, so they can't do any harm.
Known Causes of Trouble
***********************
This section describes known problems that affect users of Octave.
Most of these are not Octave bugs per se--if they were, we would fix
them. But the result for a user may be like the result of a bug.
Some of these problems are due to bugs in other software, some are
missing features that are too much work to add, and some are places
where people's opinions differ as to what is best.
* Menu:
* Actual Bugs:: Bugs we will fix later.
* Reporting Bugs::
* Bug Criteria::
* Bug Lists::
* Bug Reporting::
* Sending Patches::
* Service::
Actual Bugs We Haven't Fixed Yet
================================
* Output that comes directly from Fortran functions is not sent
through the pager and may appear out of sequence with other output
that is sent through the pager. One way to avoid this is to force
pending output to be flushed before calling a function that will
produce output from within Fortran functions. To do this, use the
command
fflush (stdout)
Another possible workaround is to use the command
page_screen_output = "false"
to turn the pager off.
* If you get messages like
Input line too long
when trying to plot many lines on one graph, you have probably
generated a plot command that is too large for `gnuplot''s
fixed-length buffer for commands. Splitting up the plot command
doesn't help because replot is implemented in gnuplot by simply
appending the new plotting commands to the old command line and
then evaluating it again.
You can demonstrate this `feature' by running gnuplot and doing
something like
plot sin (x), sin (x), sin (x), ... lots more ..., sin (x)
and then
replot sin (x), sin (x), sin (x), ... lots more ..., sin (x)
after repeating the replot command a few times, gnuplot will give
you an error.
Also, it doesn't help to use backslashes to enter a plot command
over several lines, because the limit is on the overall command
line length, once the backslashed lines are all pasted together.
Because of this, Octave tries to use as little of the command-line
length as possible by using the shortest possible abbreviations for
all the plot commands and options. Unfortunately, the length of
the temporary file names is probably what is taking up the most
space on the command line.
You can buy a little bit of command line space by setting the
environment variable `TMPDIR' to be "." before starting Octave, or
you can increase the maximum command line length in gnuplot by
changing the following limits in the file plot.h in the gnuplot
distribution and recompiling gnuplot.
#define MAX_LINE_LEN 32768 /* originally 1024 */
#define MAX_TOKENS 8192 /* originally 400 */
Of course, this doesn't really fix the problem, but it does make it
much less likely that you will run into trouble unless you are
putting a very large number of lines on a given plot.
A list of ideas for future enhancements is distributed with Octave.
See the file `PROJECTS' in the top level directory in the source
distribution.
Reporting Bugs
==============
Your bug reports play an essential role in making Octave reliable.
When you encounter a problem, the first thing to do is to see if it
is already known. *Note Trouble::. If it isn't known, then you should
report the problem.
Reporting a bug may help you by bringing a solution to your problem,
or it may not. In any case, the principal function of a bug report is
to help the entire community by making the next version of Octave work
better. Bug reports are your contribution to the maintenance of Octave.
In order for a bug report to serve its purpose, you must include the
information that makes it possible to fix the bug.
If you have Octave working at all, the easiest way to prepare a
complete bug report is to use the Octave function `bug_report'. When
you execute this function, Octave will prompt you for a subject and then
invoke the editor on a file that already contains all the configuration
information. When you exit the editor, Octave will mail the bug report
for you.
* Menu:
* Bug Criteria::
* Where: Bug Lists. Where to send your bug report.
* Reporting: Bug Reporting. How to report a bug effectively.
* Patches: Sending Patches. How to send a patch for Octave.
Have You Found a Bug?
=====================
If you are not sure whether you have found a bug, here are some
guidelines:
* If Octave gets a fatal signal, for any input whatever, that is a
bug. Reliable interpreters never crash.
* If Octave produces incorrect results, for any input whatever, that
is a bug.
* Some output may appear to be incorrect when it is in fact due to a
program whose behavior is undefined, which happened by chance to
give the desired results on another system. For example, the
range operator may produce different results because of
differences in the way floating point arithmetic is handled on
various systems.
* If Octave produces an error message for valid input, that is a bug.
* If Octave does not produce an error message for invalid input,
that is a bug. However, you should note that your idea of
"invalid input" might be my idea of "an extension" or "support for
traditional practice".
* If you are an experienced user of programs like Octave, your
suggestions for improvement are welcome in any case.
Where to Report Bugs
====================
If you have Octave working at all, the easiest way to prepare a
complete bug report is to use the Octave function `bug_report'. When
you execute this function, Octave will prompt you for a subject and then
invoke the editor on a file that already contains all the configuration
information. When you exit the editor, Octave will mail the bug report
for you.
If for some reason you cannot use Octave's `bug_report' function,
send bug reports for Octave to .
*Do not send bug reports to `help-octave'*. Most users of Octave do
not want to receive bug reports. Those that do have asked to be on the
mailing list.
As a last resort, send bug reports on paper to:
Octave Bugs c/o John W. Eaton
University of Wisconsin-Madison
Department of Chemical Engineering
1415 Engineering Drive
Madison, Wisconsin 53706 USA
How to Report Bugs
==================
Send bug reports for Octave to one of the addresses listed in *Note
Bug Lists::.
The fundamental principle of reporting bugs usefully is this:
*report all the facts*. If you are not sure whether to state a fact or
leave it out, state it!
Often people omit facts because they think they know what causes the
problem and they conclude that some details don't matter. Thus, you
might assume that the name of the variable you use in an example does
not matter. Well, probably it doesn't, but one cannot be sure.
Perhaps the bug is a stray memory reference which happens to fetch from
the location where that name is stored in memory; perhaps, if the name
were different, the contents of that location would fool the
interpreter into doing the right thing despite the bug. Play it safe
and give a specific, complete example.
Keep in mind that the purpose of a bug report is to enable someone to
fix the bug if it is not known. Always write your bug reports on the
assumption that the bug is not known.
Sometimes people give a few sketchy facts and ask, "Does this ring a
bell?" This cannot help us fix a bug. It is better to send a complete
bug report to begin with.
Try to make your bug report self-contained. If we have to ask you
for more information, it is best if you include all the previous
information in your response, as well as the information that was
missing.
To enable someone to investigate the bug, you should include all
these things:
* The version of Octave. You can get this by noting the version
number that is printed when Octave starts, or running it with the
`-v' option.
* A complete input file that will reproduce the bug.
A single statement may not be enough of an example--the bug might
depend on other details that are missing from the single statement
where the error finally occurs.
* The command arguments you gave Octave to execute that example and
observe the bug. To guarantee you won't omit something important,
list all the options.
If we were to try to guess the arguments, we would probably guess
wrong and then we would not encounter the bug.
* The type of machine you are using, and the operating system name
and version number.
* The command-line arguments you gave to the `configure' command when
you installed the interpreter.
* A complete list of any modifications you have made to the
interpreter source.
Be precise about these changes--show a context diff for them.
* Details of any other deviations from the standard procedure for
installing Octave.
* A description of what behavior you observe that you believe is
incorrect. For example, "The interpreter gets a fatal signal,"
or, "The output produced at line 208 is incorrect."
Of course, if the bug is that the interpreter gets a fatal signal,
then one can't miss it. But if the bug is incorrect output, we
might not notice unless it is glaringly wrong.
Even if the problem you experience is a fatal signal, you should
still say so explicitly. Suppose something strange is going on,
such as, your copy of the interpreter is out of synch, or you have
encountered a bug in the C library on your system. Your copy
might crash and the copy here would not. If you said to expect a
crash, then when the interpreter here fails to crash, we would
know that the bug was not happening. If you don't say to expect a
crash, then we would not know whether the bug was happening. We
would not be able to draw any conclusion from our observations.
Often the observed symptom is incorrect output when your program
is run. Unfortunately, this is not enough information unless the
program is short and simple. It is very helpful if you can
include an explanation of the expected output, and why the actual
output is incorrect.
* If you wish to suggest changes to the Octave source, send them as
context diffs. If you even discuss something in the Octave source,
refer to it by context, not by line number, because the line
numbers in the development sources probably won't match those in
your sources.
Here are some things that are not necessary:
* A description of the envelope of the bug.
Often people who encounter a bug spend a lot of time investigating
which changes to the input file will make the bug go away and
which changes will not affect it. Such information is usually not
necessary to enable us to fix bugs in Octave, but if you can find
a simpler example to report _instead_ of the original one, that is
a convenience. Errors in the output will be easier to spot,
running under the debugger will take less time, etc. Most Octave
bugs involve just one function, so the most straightforward way to
simplify an example is to delete all the function definitions
except the one in which the bug occurs.
However, simplification is not vital; if you don't want to do
this, report the bug anyway and send the entire test case you used.
* A patch for the bug. Patches can be helpful, but if you find a
bug, you should report it, even if you cannot send a fix for the
problem.
Sending Patches for Octave
==========================
If you would like to write bug fixes or improvements for Octave,
that is very helpful. When you send your changes, please follow these
guidelines to avoid causing extra work for us in studying the patches.
If you don't follow these guidelines, your information might still be
useful, but using it will take extra work. Maintaining Octave is a lot
of work in the best of circumstances, and we can't keep up unless you do
your best to help.
* Send an explanation with your changes of what problem they fix or
what improvement they bring about. For a bug fix, just include a
copy of the bug report, and explain why the change fixes the bug.
* Always include a proper bug report for the problem you think you
have fixed. We need to convince ourselves that the change is
right before installing it. Even if it is right, we might have
trouble judging it if we don't have a way to reproduce the problem.
* Include all the comments that are appropriate to help people
reading the source in the future understand why this change was
needed.
* Don't mix together changes made for different reasons. Send them
_individually_.
If you make two changes for separate reasons, then we might not
want to install them both. We might want to install just one.
* Use `diff -c' to make your diffs. Diffs without context are hard
for us to install reliably. More than that, they make it hard for
us to study the diffs to decide whether we want to install them.
Unidiff format is better than contextless diffs, but not as easy
to read as `-c' format.
If you have GNU diff, use `diff -cp', which shows the name of the
function that each change occurs in.
* Write the change log entries for your changes.
Read the `ChangeLog' file to see what sorts of information to put
in, and to learn the style that we use. The purpose of the change
log is to show people where to find what was changed. So you need
to be specific about what functions you changed; in large
functions, it's often helpful to indicate where within the
function the change was made.
On the other hand, once you have shown people where to find the
change, you need not explain its purpose. Thus, if you add a new
function, all you need to say about it is that it is new. If you
feel that the purpose needs explaining, it probably does--but the
explanation will be much more useful if you put it in comments in
the code.
If you would like your name to appear in the header line for who
made the change, send us the header line.
How To Get Help with Octave
===========================
The mailing list exists for the
discussion of matters related to using and installing Octave. If would
like to join the discussion, please send a short note to
.
*Please do not* send requests to be added or removed from the
mailing list, or other administrative trivia to the list itself.
If you think you have found a bug in the installation procedure,
however, you should send a complete bug report for the problem to
. *Note Bug Reporting::, for information
that will help you to submit a useful report.