= tiny: sh, broke, kill, rm: reduced command line interface to the
Inferno system


*tiny/sh* [ *-n* ] [ **-c**__command__ ] [ _file_ ]

*tiny/broke*

*tiny/kill* [ *-g* ] [ _pid ..._ ] [ _module ..._ ]

*tiny/rm* [ _file_ ... ]


The _tiny_ commands are smaller, simpler versions of more capable but
larger Inferno commands. They are provided for use on devices where a
certain level of functionality might be useful for configuration or
maintenance (or development), but device constraints are such as to make
the use of the normal, fleshier versions of the commands unattractive.
For example, the Dis object files can be as much as 5 times smaller (or
better) than the mainstream alternatives. They are also useful when
initially porting the system. They live in the directory */dis/tiny*,
but could be placed in the */dis* of a small device (eg, via _root_(3))·

_Broke_ kills broken processes and prints their process IDs.

_Kill_ terminates each process (for a numeric process ID _pid_) or
process running a given _module_ (for a non-numeric module name), by
writing a

message to the corresponding process's control file in _prog_(3). The
*-g* option causes _kill_ to write a

message instead, killing all processes in the given process's process
group (see _sys-pctl_(2)). Processes running a _module_ are identified
by their

file, and the process ID of each such process is printed on standard
output.

_Rm_ removes files and empty directories, subject to the permission
rules given in _rm_(1). There are no options.

_Sh_ provides a simple user level interface (a shell) to the Inferno
system. (It was once the only Inferno shell.) It reads input lines,
identifies a command and arguments for that command, and arranges for
execution of the corresponding Inferno module. There are features that
allow input/output redirection, creating pipelines, and performing tasks
in background. It is nevertheless a rudimentary shell designed for
starting and debugging applications. It is not intended to serve as a
general-purpose programmable shell.

If a file is named as a command line argument, that file is the source
of input; otherwise, standard input is read.

Options are:

*-n*::
  Don't fork the namespace. By default, _sh_ forks the namespace, making
  subsequent namespace changes invisible to the previous namespace
  group.
**-c**__command__::
  Execute the single _command_ rather than prompting to read commands
  from the standard input.

== Command line syntax

Each line consists of one or more command pipelines each separated by
either an ampersand (&) which indicates that the pipeline should be run
in background or a semi-colon (;). The semi-colon need not be provided
for the last command pipeline on a line.

Command pipelines are not allowed to span lines.

Each command pipeline consists of one or more commands separated by a
vertical bar (*|*) character. The standard output of one command is made
the standard input of the next command to the right.

Redirection of input/output to pipes takes precedence over redirection
from/to files.

In the limit case, a command pipeline consists of a single command with
no pipes.

A command consists of one or more fields. The first (leftmost) field is
the command field. It is used to determined the executable file to be
loaded and run; see below. The remaining fields are parsed and become
command line arguments that are passed to the module's init function as
a list of strings.

Any input following a *#* on a line is discarded as comment.

== Finding the module

The command field is converted to the pathname of the Dis file of some
module. That field can be either an absolute pathname, starting from
*/*, or a relative pathname from the current directory.

As a convenience, the user need not specify the *.dis* suffix to the
filename. If missing, it will be added by the shell.

If the load fails there is, in general, a second attempt to load the
module by resolving the pathname relative to the */dis* directory (or
any directory bound to the */dis* directory in the current namespace).

There are two exceptions to this second attempt. The second load attempt
is not performed if the command field provides an absolute pathname or a
relative pathname starting with dot-slash (*./*). Such explicit naming
is taken to mean that the user will accept no substitutions.

The shell requires that the Dis file implement a module with an
interface equivalent to the

module as specified in */module/sh.m* (see _command_(2)). Otherwise, the
named file will not load.

In lieu of a path mechanism, a process can create a union directory at
*/dis*.

== File name expansion

Command line arguments (including the command field itself) are expanded
by the shell according to the regular expression rules described in
_filepat_(2).

This expansion is not applied to the filenames used for input/output
redirection.

== Quoting

The shell special characters can be stripped of their meaning and
treated as literals by enclosing them in single quotes. Inside a quoted
string, the special meaning of the single quote can be removed by
immediately following it with another single quote. Command lines with
un-terminated quoted strings are rejected and cause an error message.

For example:

....
$ echo ''''
'
$ echo 'don''t'
don't
$ echo 'hello' 'world
sh: unmatched quote
$ echo 'a'b
ab
$ echo a'b'
ab
$
....

== Shell special characters

The following characters are treated specially by _sh_ and must be
quoted to be taken literally:

blank::
  white space, except in a quoted string
tab::
  white space, except in a quoted string
newline::
  command line terminator
*#*::
  Start of comment
*'*::
  Start of/end of quoted string (single quote)
*|*::
  Interface between commands in a command pipeline.
*&*::
  Terminator for command pipelines to be run in background.
*;*::
  Terminator for command pipelines to be run synchronously by the shell.
*>*::
  Output re-direction: create file if it does not exist; truncate file
  if it exists
*>>*::
  Output re-direction: create file if it does not exist; append to file
  if it exists
*<*::
  Input re-direction.

== Prompt

The shell uses a prompt consisting of the system name as provided by
*/dev/sysname* suffixed by *$*.

== Input/output re-directions

By default, standard input is the console keyboard and standard output
the console display. Each command can specify that standard input be
taken from a file and standard output be written to a file.

Attempts to redirect standard input to a non-existing file will fail.
Redirecting standard output to a non-existing file will cause that file
to be created. If the destination file already exists, it will be
overwritten. Any previous contents are lost.

In cases of competing re-direction mechanisms (re-direct to a file and
to a pipe), the pipe has precedence.

== Background tasks

In general, the shell waits for the termination of a command pipeline
before continuing execution, for example, prompting the user for the
next command. However, if the command pipeline is terminated by an
ampersand (*&*) character, the wait stage is skipped and the shell
continues execution immediately, in this case the command pipeline
executes as a background task.

== Name space concerns

When started, the shell creates an independent file name space that is a
copy of the file name space of the shell's creator.

Command pipelines started by the shell are executed by threads that
share the shell's name space. If those commands modify the file name
space (and they have not mimicked the shell in creating their own
independent name space), those modifications will be perceived by the
shell when it continues execution. See _bind_(1) and _sys-pctl_(2).

== FILES

**/prog/**__n__*/wait*

== SOURCE

*/appl/tiny/broke.b* +
*/appl/tiny/kill.b* +
*/appl/tiny/rm.b* +
*/appl/tiny/sh.b*

== SEE ALSO

_bind_(1), _sh_(1), _filepat_(2), _command_(2), _sys-pctl_(2),
_cons_(3), _pipe_(3), _prog_(3)