csh.1

早期freebsd实现

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.\"     @(#)csh.1	8.2 (Berkeley) 1/21/94
.\"
.Dd January 21, 1994
.Dt CSH 1
.Os BSD 4
.Sh NAME
.Nm csh
.Nd a shell (command interpreter) with C-like syntax
.Sh SYNOPSIS
.Nm csh
.Op Fl bcefinstvVxX
.Op arg ...
.Nm csh
.Op Fl l
.Sh DESCRIPTION
The
.Nm csh
is a command language interpreter
incorporating a history mechanism (see
.Nm History Substitutions ) ,
job control facilities (see
.Nm Jobs ) ,
interactive file name
and user name completion (see
.Nm File Name Completion ) ,
and a C-like syntax. It is used both as an interactive
login shell and a shell script command processor.
.Ss Argument list processing
If the first argument (argument 0) to the shell is
.Ql Fl \& ,
then this is a login shell.
A login shell also can be specified by invoking the shell with the 
.Ql Fl l
flag as the only argument.
.Pp
The rest of the flag arguments are interpreted as follows:
.Bl -tag -width 5n
.It Fl b
This flag forces a ``break'' from option processing, causing any further
shell arguments to be treated as non-option arguments.
The remaining arguments will not be interpreted as shell options.
This may be used to pass options to a shell script without confusion
or possible subterfuge.
The shell will not run a set-user ID script without this option.
.It Fl c
Commands are read from the (single) following argument which must
be present.
Any remaining arguments are placed in
.Ar argv .
.It Fl e
The shell exits if any invoked command terminates abnormally
or yields a non-zero exit status.
.It Fl f
The shell will start faster, because it will neither search for nor
execute commands from the file
.Pa \&.cshrc
in the invoker's home directory.
.It Fl i
The shell is interactive and prompts for its top-level input,
even if it appears not to be a terminal.
Shells are interactive without this option if their inputs
and outputs are terminals.
.It Fl l
The shell is a login shell (only applicable if
.Fl l
is the only flag specified).
.It Fl n
Commands are parsed, but not executed.
This aids in syntactic checking of shell scripts.
.It Fl s
Command input is taken from the standard input.
.It Fl t
A single line of input is read and executed.
A
.Ql \e
may be used to escape the newline at the end of this
line and continue onto another line.
.It Fl v
Causes the
.Ar verbose
variable to be set, with the effect
that command input is echoed after history substitution.
.It Fl x
Causes the
.Ar echo
variable to be set, so that commands are echoed immediately before execution.
.It Fl V
Causes the
.Ar verbose
variable to be set even before
.Pa .cshrc
is executed.
.It Fl X
Is to
.Fl x
as
.Fl V
is to
.Fl v .
.El
.Pp
After processing of flag arguments, if arguments remain but none of the
.Fl c ,
.Fl i ,
.Fl s ,
or
.Fl t
options were given, the first argument is taken as the name of a file of
commands to be executed.
The shell opens this file, and saves its name for possible resubstitution
by `$0'.
Since many systems use either the standard version 6 or version 7 shells
whose shell scripts are not compatible with this shell, the shell will
execute such a `standard' shell if the first character of a script
is not a `#', i.e., if the script does not start with a comment.
Remaining arguments initialize the variable
.Ar argv .
.Pp
An instance of
.Nm csh
begins by executing commands from the file
.Pa /etc/csh.cshrc
and,
if this is a login shell,
.Pa \&/etc/csh.login .
It then executes
commands from
.Pa \&.cshrc
in the
.Ar home
directory of the invoker, and, if this is a login shell, the file
.Pa \&.login
in the same location.
It is typical for users on crt's to put the command ``stty crt''
in their
.Pa \&.login
file, and to also invoke
.Xr tset  1
there.
.Pp
In the normal case, the shell will begin reading commands from the
terminal, prompting with `% '.
Processing of arguments and the use of the shell to process files
containing command scripts will be described later.
.Pp
The shell repeatedly performs the following actions:
a line of command input is read and broken into
.Ar words  .
This sequence of words is placed on the command history list and parsed.
Finally each command in the current line is executed.
.Pp
When a login shell terminates it executes commands from the files
.Pa .logout
in the user's
.Ar home
directory and
.Pa /etc/csh.logout .
.Ss Lexical structure
The shell splits input lines into words at blanks and tabs with the
following exceptions.
The characters
`&' `\&|' `;' `<' `>' `(' `)'
form separate words.
If doubled in `&&', `\&|\&|', `<<' or `>>' these pairs form single words.
These parser metacharacters may be made part of other words, or prevented their
special meaning, by preceding them with `\e'.
A newline preceded by a `\e' is equivalent to a blank.
.Pp
Strings enclosed in matched pairs of quotations,
`'\|', `\*(ga' or `"',
form parts of a word; metacharacters in these strings, including blanks
and tabs, do not form separate words.
These quotations have semantics to be described later.
Within pairs of `\'' or `"' characters, a newline preceded by a `\e' gives
a true newline character.
.Pp
When the shell's input is not a terminal,
the character `#' introduces a comment that continues to the end of the
input line.
It is prevented this special meaning when preceded by `\e'
and in quotations using `\`', `\'', and `"'.
.Ss Commands
A simple command is a sequence of words, the first of which
specifies the command to be executed.
A simple command or
a sequence of simple commands separated by `\&|' characters
forms a pipeline.
The output of each command in a pipeline is connected to the input of the next.
Sequences of pipelines may be separated by `;', and are then executed
sequentially.
A sequence of pipelines may be executed without immediately
waiting for it to terminate by following it with an `&'.
.Pp
Any of the above may be placed in `(' `)' to form a simple command (that
may be a component of a pipeline, etc.).
It is also possible to separate pipelines with `\&|\&|' or `&&' showing,
as in the C language,
that the second is to be executed only if the first fails or succeeds
respectively. (See
.Em Expressions . )
.Ss Jobs
The shell associates a
.Ar job
with each pipeline.  It keeps
a table of current jobs, printed by the
.Ar jobs
command, and assigns them small integer numbers.  When
a job is started asynchronously with `&', the shell prints a line that looks
like:
.Bd -filled -offset indent
.Op 1
1234
.Ed
.Pp
showing that the job which was started asynchronously was job number
1 and had one (top-level) process, whose process id was 1234.
.Pp
If you are running a job and wish to do something else you may hit the key
.Nm ^Z
(control-Z) which sends a STOP signal to the current job.
The shell will then normally show that the job has been `Stopped',
and print another prompt.  You can then manipulate the state of this job,
putting it in the
.Em background
with the
.Ar bg
command, or run some other
commands and eventually bring the job back into the foreground with
the
.Em foreground
command
.Ar fg  .
A
.Nm ^Z
takes effect immediately and
is like an interrupt in that pending output and unread input are discarded
when it is typed.  There is another special key
.Nm ^Y
that does not generate a STOP signal until a program attempts to
.Xr read  2
it.
This request can usefully be typed ahead when you have prepared some commands
for a job that you wish to stop after it has read them.
.Pp
A job being run in the background will stop if it tries to read
from the terminal.  Background jobs are normally allowed to produce output,
but this can be disabled by giving the command ``stty tostop''.
If you set this
tty option, then background jobs will stop when they try to produce
output like they do when they try to read input.
.Pp
There are several ways to refer to jobs in the shell.  The character
`%' introduces a job name.  If you wish to refer to job number 1, you can
name it as `%1'.  Just naming a job brings it to the foreground; thus
`%1' is a synonym for `fg %1', bringing job number 1 back into the foreground.
Similarly saying `%1 &' resumes job number 1 in the background.
Jobs can also be named by prefixes of the string typed in to start them,
if these prefixes are unambiguous, thus `%ex' would normally restart
a suspended
.Xr ex  1
job, if there were only one suspended job whose name began with
the string `ex'.  It is also possible to say `%?string'
which specifies a job whose text contains
.Ar string ,
if there is only one such job.
.Pp
The shell maintains a notion of the current and previous jobs.
In output about jobs, the current job is marked with a `+'
and the previous job with a `\-'.  The abbreviation `%+' refers
to the current job and `%\-' refers to the previous job.  For close
analogy with the syntax of the
.Ar history
mechanism (described below),
`%%' is also a synonym for the current job.
.Pp
The job control mechanism requires that the
.Xr stty 1
option
.Ic new
be set. It is an artifact from a
.Em new
implementation
of the
tty driver that allows generation of interrupt characters from
the keyboard to tell jobs to stop.  See stty(1) for details
on setting options in the new tty driver.
.Ss Status reporting
This shell learns immediately whenever a process changes state.
It normally informs you whenever a job becomes blocked so that
no further progress is possible, but only just before it prints
a prompt.  This is done so that it does not otherwise disturb your work.
If, however, you set the shell variable
.Ar notify ,
the shell will notify you immediately of changes of status in background
jobs.
There is also a shell command
.Ar notify
that marks a single process so that its status changes will be immediately
reported.  By default
.Ar notify
marks the current process;
simply say `notify' after starting a background job to mark it.
.Pp
When you try to leave the shell while jobs are stopped, you will
be warned that `You have stopped jobs.'  You may use the
.Ar jobs
command to see what they are.  If you do this or immediately try to
exit again, the shell will not warn you a second time, and the suspended
jobs will be terminated.
.Ss File Name Completion
When the file name completion feature is enabled by setting
the shell variable
.Ar filec
(see
.Ic set ) ,
.Nm csh
will
interactively complete file names and user names from unique
prefixes, when they are input from the terminal followed by
the escape character (the escape key, or control-[)
For example,
if the current directory looks like
.Bd -literal -offset indent
DSC.OLD  bin      cmd      lib      xmpl.c
DSC.NEW  chaosnet cmtest   mail     xmpl.o
bench    class    dev      mbox     xmpl.out
.Ed
.Pp
and the input is
.Pp
.Dl % vi ch<escape>
.Pp
.Nm csh
will complete the prefix ``ch''
to the only matching file name ``chaosnet'', changing the input
line to
.Pp
.Dl % vi chaosnet
.Pp
However, given
.Pp
.Dl % vi D<escape>
.Pp
.Nm csh
will only expand the input to
.Pp
.Dl % vi DSC.
.Pp
and will sound the terminal bell to indicate that the expansion is
incomplete, since there are two file names matching the prefix ``D''.
.Pp
If a partial file name is followed by the end-of-file character
(usually control-D), then, instead of completing the name,
.Nm csh
will list all file names matching the prefix.  For example,
the input
.Pp
.Dl % vi D<control-D>
.Pp
causes all files beginning with ``D'' to be listed:
.Pp
.Dl DSC.NEW	DSC.OLD
.Pp
while the input line remains unchanged.
.Pp
The same system of escape and end-of-file can also be used to
expand partial user names, if the word to be completed
(or listed) begins with the character ``~''.  For example,
typing
.Pp
.Dl cd ~ro<escape>
.Pp
may produce the expansion
.Pp
.Dl cd ~root
.Pp
The use of the terminal bell to signal errors or multiple matches
can be inhibited by setting the variable
.Ar nobeep  .
.Pp
Normally, all files in the particular directory are candidates
for name completion.  Files with certain suffixes can be excluded
from consideration by setting the variable
.Ar fignore
to the
list of suffixes to be ignored.  Thus, if
.Ar fignore
is set by
the command
.Pp