| Execution method: | Interpreted |
|---|---|
| Lang tag(s): | csh |
| See Also: |
csh was the shell that William Joy wrote forBSD.csh accepted the sameUnix commands as other shells, but had a very different syntax (for variable assignments, control flow, and such).csh is not compatible with theBourne Shell.
BSD keeps the C Shell at/bin/csh.Hashbang lines should use the -f option:
<lang csh>#!/bin/csh -f</lang>
C Shell is obsolete.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 (ls ~), job control, command history, and aliases, but POSIX shells now have all of those.
Csh Programming Considered Harmful andTop Ten Reasons not to use the C shell give multiple reasons to avoid C Shell.
tcsh is a later version that fixed many of the problems with csh. It is still actively, if intermittently, maintained and has a following such as on Solaris.
The manual for csh(1) claims that C Shell has "a C-like syntax". Several other languages have a C-like syntax, includingJava andPike, and Unix utilitiesAWK andbc. C Shell is less likeC than those other languages.
This example prints aHailstone sequence from 13.
| C | C Shell |
|---|---|
| <lang c>#include <stdio.h> intmain(){ int n; n = 13; printf("%d\n", n); while (n != 1) { if (n % 2) n = 3 * n + 1; else n /= 2; printf("%d\n", n); }return 0; }</lang> | <lang csh>
if ($n % 2) then @ n = 3 * $n + 1 else @ n /= 2 endif echo $n end
|
C Shell has no braces {} to group the commands. Strange keywords arethen,endif andend. Expressions have$n instead ofn. Assignments use@ n.
C Shell has "a C-like syntax" because C Shell is more like C thanBourne Shell.
| Bourne Shell | C Shell |
|---|---|
| <lang bash>n=13 echo $nwhile test $n -ne 1; do if expr $n % 2 >/dev/null; then n=`expr 3 \* $n + 1` else n=`expr $n / 2` fi echo $n done</lang> | <lang csh>@ n = 13 echo $nwhile ($n != 1) if ($n % 2) then @ n = 3 * $n + 1 else @ n /= 2 endif echo $n end</lang> |
Bourne Shell requirestest orexpr 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, so10 - 3 - 2 acts like10 - (3 - 2). The fix is to use parentheses.
<lang csh>% @ n = 10 - 3 - 2% echo $n9% @ n = (10 - 3) - 2% echo $n5</lang>
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The following 31 pages are in this category, out of 31 total.