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1.1 root 1: .TH NEWCSH 1
2: .UC 4
3: .bd S 3
4: .SH NAME
5: newcsh \- description of new csh features (over oldcsh)
6: .SH SYNOPSIS
7: .B csh
8: \fIcsh-options\fR
9: .SH SUMMARY
10: This is a summary of features new in
11: .IR csh (1)
12: in this version of the system; an older version of
13: .I csh
14: is available as
15: .I oldcsh.
16: This newer
17: .I csh
18: has some new process control primitives and a few other new features.
19: Users of
20: .I csh
21: must (and automatically) use the new terminal driver (summarized in
22: .IR newtty(4)
23: and completely described with the old in
24: .IR tty (4))
25: which allows generation of some new
26: interrupt signals from the keyboard which tell jobs to stop,
27: and arbitrates access to the terminal;
28: on CRT's the command ``stty crt'' is
29: normally placed in the
30: .I .login
31: file to be executed at login,
32: to set other useful modes of this terminal driver.
33: .PP
34: .B "Jobs."
35: .PP
36: The most important new feature in this shell is the control of
37: .I jobs.
38: A job is associated with each pipeline, where a pipeline is either
39: a simple command like ``date'', or a pipeline like ``who | wc''.
40: The shell keeps a table of current jobs, and assigns them small
41: integer numbers.
42: When you start a job in the background, the shell prints a line
43: which looks like:
44: .PP
45: \ \ \ \ [1] 1234
46: .PP
47: this indicating that the job which was started asynchronously with ``&''
48: is job number 1 and has one (top-level) process, whose process id is 1234.
49: The set of current jobs is listed by the
50: .I jobs
51: command.
52: .PP
53: If you are running a job and wish to do something else you may hit the
54: key ^Z (control-Z) which sends a
55: .I stop
56: signal to the current job. The shell will then normally indicate that
57: the job has been ``Stopped'', and print another prompt.
58: You can then
59: put the job in the background with the command ``bg'', or run
60: some other commands and then return the job to the foreground with
61: ``fg''.
62: A ^Z takes effect immediately and is like an interrupt in that
63: pending output and unread input are discarded when it is typed.
64: There is another special key ^Y which does not generate a stop signal
65: until a program attempts to
66: .IR read (2)
67: it.
68: This can usefully be typed ahead when you have prepared some commands
69: for a job which you wish to stop after it has read them.
70: .PP
71: A job being run in the background will stop if it tries to read
72: from the terminal. Background jobs are normally allowed to produce output,
73: but this can be disabled by doing ``stty tostop''. If you set this
74: tty option, then background jobs will stop when they try to produce
75: output like they do when they try to read input.
76: .PP
77: There are several ways to refer to jobs in the shell. The character
78: ``%'' introduces a job name. If you wish to refer to job number 1, you can
79: name it as ``%1''. Just naming a job brings it to the foreground; thus
80: ``%1'' is a synonym for ``fg %1'', bringing job 1 back into the foreground.
81: Similarly saying ``%1 &'' resumes job 1 in the background.
82: Jobs can also be named by prefixes of the string typed in to start them,
83: if these prefixes are unambiguous, thus ``%ex'' would normally restart
84: a suspended
85: .IR ex (1)
86: job, if there were only one suspended job whose name began with
87: the string ``ex''. It is also possible to say ``%?string''
88: which specifies a job whose text contains
89: .I string,
90: if there is only one such job.
91: .PP
92: The shell also maintains a notion of the current and previous jobs.
93: In output pertaining to jobs, the current job is marked with a ``+''
94: and the previous job with a ``\-''. The abbreviation ``%+'' refers
95: to the current job and ``%\-'' refers to the previous job. For close
96: analogy with the
97: .I history
98: mechanism,
99: ``%%'' is also a synonym for the current job.
100: .PP
101: .B "Status reporting."
102: .PP
103: This shell learns immediately whenever a process changes state.
104: It normally informs you whenever a job becomes blocked so that
105: no further progress is possible, but only just before it prints
106: a prompt. This is done so that it does not otherwise disturb your work.
107: If, however, you set the shell variable
108: .I notify,
109: the shell will notify you immediately of changes of status in background
110: jobs.
111: There is also a shell command
112: .I notify
113: which marks a single process so that its status changes will be immediately
114: reported. By default
115: .I notify
116: marks the current process;
117: simply say ``notify'' after starting a background job to mark it.
118: .PP
119: When you try to leave the shell while jobs are stopped, you will
120: be warned that ``You have stopped jobs.'' You may use the ``jobs''
121: command to see what they are. If you do this or immediately try to
122: exit again, the shell will not warn you a second time, and the suspended
123: jobs will be unmercifully terminated.
124: .PP
125: .B "New builtin commands."
126: .HP 5
127: .B bg
128: .br
129: .ns
130: .HP 5
131: \fBbg\ %\fRjob\ ...
132: .br
133: Puts the current or specified jobs into the background, continuing them
134: if they were stopped.
135: .HP 5
136: .B fg
137: .br
138: .ns
139: .HP 5
140: \fBfg\ %\fRjob\ ...
141: .br
142: Brings the current or specified jobs into the foreground, continuing them if
143: they were stopped.
144: .HP 5
145: .B jobs
146: .br
147: .ns
148: .HP 5
149: .B "jobs \-l"
150: .br
151: Lists the active jobs; given the
152: .B \-l
153: options lists process id's in addition to the normal information.
154: .HP 5
155: \fBkill %\fRjob
156: .br
157: .ns
158: .HP 5
159: \fBkill\ \-\fRsig\ \fB%\fRjob\ ...
160: .br
161: .ns
162: .HP 5
163: \fBkill\fR\ pid
164: .br
165: .ns
166: .HP 5
167: \fBkill\ \-\fRsig\ pid\ ...
168: .br
169: .ns
170: .HP 5
171: \fBkill\ \-l\fR
172: .br
173: Sends either the TERM (terminate) signal or the
174: specified signal to the specified jobs or processes.
175: Signals are either given by number or by names (as given in
176: .I /usr/include/signal.h,
177: stripped of the prefix ``SIG'').
178: The signal names are listed by ``kill \-l''.
179: There is no default, saying just `kill' does not
180: send a signal to the current job.
181: If the signal being sent is TERM (terminate) or HUP (hangup),
182: then the job or process will be sent a CONT (continue) signal as well.
183: .HP 5
184: .B notify
185: .br
186: .ns
187: .HP 5
188: \fBnotify\ %\fRjob\ ...
189: .br
190: Causes the shell to notify the user asynchronously when the status of the
191: current or specified jobs changes; normally notification is presented
192: before a prompt. All jobs are marked ``notify'' if the shell variable
193: ``notify'' is set.
194: .HP 5
195: \fBstop\ %\fRjob\ ...
196: .br
197: Stops the specified job which is executing in the background.
198: .HP 5
199: \fB%\fRjob
200: .br
201: Brings the specified job into the foreground.
202: .HP 5
203: \fB%\fRjob \fB&\fR
204: .br
205: Continues the specified job in the background.
206: .br
207: .ne 5
208: .PP
209: .B "Process limitations."
210: .PP
211: The shell provides access to an experimental facility for limiting
212: the consumption by a single process of system resources.
213: The following commands control this facility:
214: .HP 5
215: \fBlimit\fR \fIresource\fR \fImaximum-use\fR
216: .HP 5
217: \fBlimit\fR \fIresource\fR
218: .br
219: .ns
220: .HP
221: \fBlimit\fR
222: .br
223: Limits the consumption by the current process and each process
224: it creates to not individually exceed \fImaximum-use\fR on the
225: specified \fIresource\fR. If no \fImaximum-use\fR is given, then
226: the current limit is printed; if no \fIresource\fR is given, then
227: all limitations are given.
228: .IP
229: Resources controllable currently include \fIcputime\fR (the maximum
230: number of cpu-seconds to be used by each process), \fIfilesize\fR
231: (the largest single file which can be created), \fIdatasize\fR
232: (the maximum growth of the data+stack region via
233: .IR sbrk (2)
234: beyond the end of the program text), \fIstacksize\fR (the maximum
235: size of the automatically-extended stack region), and \fIcoredumpsize\fR
236: (the size of the largest core dump that will be created).
237: .IP
238: The \fImaximum-use\fR may be given as a (floating point or integer)
239: number followed by a scale factor. For all limits other than \fIcputime\fR
240: the default scale is ``k'' or ``kilobytes'' (1024 bytes);
241: a scale factor of ``m'' or ``megabytes'' may also be used.
242: For cputime the default scaling is ``seconds'', while ``m'' for minutes
243: or ``h'' for hours, or a time of the form ``mm:ss'' giving minutes
244: and seconds may be used.
245: .IP
246: For both \fIresource\fR names and scale factors, unambiguous prefixes
247: of the names suffice.
248: .HP 5
249: \fBunlimit\fR \fIresource\fR
250: .br
251: .ns
252: .HP 5
253: \fBunlimit\fR
254: .br
255: Removes the limitation on \fIresource\fR. If no \fIresource\fR
256: is specified, then all \fIresource\fR limitations are removed.
257: .ne 5
258: .PP
259: .B "Directory stack."
260: .PP
261: This shell now keeps track of the current directory (which is kept
262: in the variable
263: .I cwd)
264: and also maintains a stack of directories, which is printed by the
265: command
266: .I dirs.
267: You can change to a new directory and push down the old directory
268: stack by using the command
269: .I pushd
270: which is otherwise like the
271: .I chdir
272: command, changing to its argument.
273: You can pop the directory stack by saying
274: .I popd.
275: Saying
276: .I pushd
277: with no arguments exchanges the top two elements of the directory stack.
278: The elements of the directory stack are numbered from 1 starting at the top.
279: Saying
280: .I pushd
281: with a argument ``+\fIn\fR'' rotates the directory stack to make that entry
282: in the stack be at the top and changes to it.
283: Giving
284: .I popd
285: a ``+\fIn\fR'' argument eliminates that argument from the directory stack.
286: .PP
287: .B "Miscellaneous."
288: .PP
289: This shell imports the environment variable USER into the variable
290: .I user,
291: TERM into
292: .I term,
293: and
294: HOME into
295: .I home,
296: and exports these back into the environment whenever the normal
297: shell variables are reset.
298: The environment variable PATH is likewise handled; it is not
299: necessary to worry about its setting other than in the file
300: .I \&.cshrc
301: as inferior
302: .I csh
303: processes will import the definition of
304: .I path
305: from the environment, and re-export it if you then change it.
306: (It could be set once in the
307: .I \&.login
308: except that commands over the Berknet would not
309: see the definition.)
310: .PP
311: There are new commands
312: .I eval,
313: which is like the eval of the Bourne shell
314: .IR sh (1),
315: and useful with
316: .IR tset (1),
317: and
318: .I suspend
319: which stops a shell (as though a ^Z had stopped it; since
320: shells normally ignore ^Z signals, this command is necessary.)
321: .PP
322: There is a new variable
323: .I cdpath;
324: if set, then each directory in
325: .I cdpath
326: will be searched for a directory named in a
327: .I chdir
328: command if there is no such subdirectory of the current directory.
329: .PP
330: An
331: .I unsetenv
332: command removing environment variables has been added.
333: .PP
334: There is a new ``:'' modifier ``:e'', which yields the extension
335: portion of a filename. Thus if ``$a'' is ``file.c'', ``$a:e'' is ``c''.
336: .PP
337: There are two new operators in shell expressions ``!~'' and ``=~'' which
338: are like the string operations ``!='' and ``=='' except that the right
339: hand side is a
340: .I pattern
341: (containing, e.g. ``*''s, ``?''s and instances of ``[...]'')
342: against which the left hand operand is matched. This reduces the
343: need for use of the
344: .I switch
345: statement in shell scripts when all that is really needed is pattern matching.
346: .PP
347: The form ``$<'' is new, and is replaced by a line from the standard
348: input, with no further interpretation thereafter. It may therefore
349: be used to read from the keyboard in a shell script.
350: .SH "SEE ALSO"
351: csh(1), killpg(2), sigsys(2), signal(2), jobs(3), sigset(3), tty(4)
352: .SH BUGS
353: Command sequences of the form ``a ; b ; c'' are not handled gracefully
354: when stopping is attempted. If you suspend ``b'', the shell will then
355: immediately execute ``c''. This is especially noticeable if this
356: expansion results from an
357: .I alias.
358: It suffices to place the sequence of commands in ()'s to force it to
359: a subshell, i.e. ``( a ; b ; c )'', but see the next bug.
360: .PP
361: Shell builtin functions are not stoppable/restartable.
362: .PP
363: Control over output is primitive;
364: perhaps this will inspire someone to work on a good virtual
365: terminal interface. In a virtual terminal interface much more
366: interesting things could be done with output control.
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