Category:C Shell: Difference between revisions
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(Copy text from C Shell. Wiki prevents move to 'Category:' namespace. Authors: Kernigh and Dkf. http://rosettacode.org/mw/index.php?title=C_Shell&action=history) |
(Fill 'Syntax' and 'Reputation' sections.) |
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{{language |
{{language |
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|tags=csh}}{{implementation|UNIX Shell}} |
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'''csh''' was the shell that William Joy wrote for [[BSD]]. '''csh''' accepted the same [[Unix]] commands as other shells, but had a very different syntax (for variable assignments, control flow, and such). '''csh''' is not compatible with the [[Bourne Shell]]. |
'''csh''' was the shell that William Joy wrote for [[BSD]]. '''csh''' accepted the same [[Unix]] commands as other shells, but had a very different syntax (for variable assignments, control flow, and such). '''csh''' is not compatible with the [[Bourne Shell]]. |
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BSD keeps the C |
BSD keeps the C Shell at <code>/bin/csh</code>. [[Hashbang]] lines should use the -f option: |
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[[Hashbang]] lines for C shell scripts should use the -f option: |
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<lang csh>#!/bin/csh -f</lang> |
<lang csh>#!/bin/csh -f</lang> |
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== Reputation == |
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C Shell is obsolete. Most scriptwriters prefer a Bourne-compatible shell, and few users want to learn two flavors of shells. C Shell introduced tilde expansion (<code>ls ~</code>), history recall, job control and aliases, but POSIX shells now have all of those. |
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== Syntax == |
== Syntax == |
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[http://www.openbsd.org/cgi-bin/man.cgi?query=csh&apropos=0&sektion=1&manpath=OpenBSD+Current&arch=i386&format=html The manual for csh(1)] claims that C Shell has "a C-like syntax". Several other languages have a C-like syntax, including [[Java]] and [[Pike]], and Unix utilities [[AWK]] and [[bc]]. C Shell is less like [[C]] than those other languages. |
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{| class="wikitable" style="clear: right; width: 100%" |
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This example prints a [[Hailstone sequence]] from 13. |
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{| class="wikitable" |
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! C |
! C |
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! C Shell |
! C Shell |
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|- |
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|| <lang c>#include <stdio.h> |
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</lang> |
</lang> |
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|} |
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C Shell has no braces {} to group the commands. Strange keywords are <code>then</code>, <code>endif</code> and <code>end</code>. Expressions have <code>$n</code> instead of <code>n</code>. Assignments use <code>@ n</code>. |
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C Shell has "a C-like syntax" because C Shell is more like C than [[Bourne Shell]]. |
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{| class="wikitable" |
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n=13 |
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! C Shell |
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|- |
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echo $n |
echo $n |
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while test $n -ne 1; do |
while test $n -ne 1; do |
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fi |
fi |
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echo $n |
echo $n |
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done |
done</lang> |
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echo $n |
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while ($n != 1) |
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if ($n % 2) then |
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@ n = 3 * $n + 1 |
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else |
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@ n /= 2 |
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endif |
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echo $n |
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|} |
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Bourne Shell requires <code>test</code> or <code>expr</code> to evaluate expressions. C Shell has built-in expressions, so the Hailstone sequence comes more easily. These expressions have a stupid quirk: all operators are right-associative, so <code>10 - 3 - 2</code> acts like <code>10 - (3 - 2)</code>. The fix is to use parentheses. |
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<lang csh>% @ n = 10 - 3 - 2 |
<lang csh>% @ n = 10 - 3 - 2 |
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% echo $n |
% echo $n |
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9 |
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9</lang> |
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% @ n = (10 - 3) - 2 |
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% echo $n |
% echo $n |
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5</lang> |
5</lang> |
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== Links == |
== Links == |
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* [http://www.openbsd.org/cgi-bin/man.cgi?query=csh&apropos=0&sektion=1&manpath=OpenBSD+Current&arch=i386&format=html csh(1) manual] |
* [[OpenBSD]] has [http://www.openbsd.org/cgi-bin/man.cgi?query=csh&apropos=0&sektion=1&manpath=OpenBSD+Current&arch=i386&format=html csh(1) manual] and [http://www.openbsd.org/cgi-bin/cvsweb/src/bin/csh/ source code]. |
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* [http://www.grymoire.com/Unix/CshTop10.txt Top Ten Reasons not to use the C shell] |
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