TINY(1) TINY(1)
NAME
tiny: sh, rm - reduced command line interface to the Inferno
system
SYNOPSIS
tiny/sh [ -n ] [ -ccommand ] [ file ]
tiny/rm [ file ... ]
DESCRIPTION
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 are typically 5 times smaller
(or better) than the mainstream alternatives. They live in
the directory /dis/tiny, but could be placed in the /dis of
a small device (eg, via root(3))ยท
Rm removes files and empty directories, subject to the per-
mission 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 correspond-
ing 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 invisi-
ble to the previous namespace group.
-ccommand
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
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the pipeline should be run in background or a semi-colon
(;). The semi-colon need not be provided for the last com-
mand pipeline on a line.
Command pipelines are not allowed to span lines.
Each command pipeline consists of one or more commands sepa-
rated by a vertical bar (|) character. The standard output
of one command is made the standard input of the next com-
mand 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 (left-
most) 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 argu-
ments 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 `Command' 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
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directory at /dis.
File name expansion
Command line arguments (including the command field itself)
are expanded by the shell according to the regular expres-
sion 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 mean-
ing 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 back-
ground.
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; Terminator for command pipelines to be run syn-
chronously 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 stan-
dard 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 pipe-
line is terminated by an ampersand (&) character, the wait
stage is skipped and the shell continues execution immedi-
ately, in this case the command pipeline executes as a back-
ground 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 contin-
ues execution. See bind(1) and sys-pctl(2).
FILES
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/prog/n/wait
SOURCE
/appl/tiny/sh.b
/appl/tiny/rm.b
SEE ALSO
bind(1), sh(1), filepat(2), command(2), sys-pctl(2),
cons(3), pipe(3), prog(3)
BUGS
Inferno does not support an append mode. Therefore, the
shell's approximation is not guaranteed if there are concur-
rent appending processes.
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