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author | rgrimes <rgrimes@FreeBSD.org> | 1994-05-26 06:18:55 +0000 |
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committer | rgrimes <rgrimes@FreeBSD.org> | 1994-05-26 06:18:55 +0000 |
commit | e3cfc8ce61f788739c66445d903f8beacb40c93d (patch) | |
tree | ba7beef9ee9289c4383bad976f88710e44c98b4d /bin/csh/USD.doc/csh.4 | |
parent | 862fdf11a2ede45dec0da01ed575525d79468981 (diff) | |
download | FreeBSD-src-e3cfc8ce61f788739c66445d903f8beacb40c93d.zip FreeBSD-src-e3cfc8ce61f788739c66445d903f8beacb40c93d.tar.gz |
BSD 4.4 Lite bin Sources
Diffstat (limited to 'bin/csh/USD.doc/csh.4')
-rw-r--r-- | bin/csh/USD.doc/csh.4 | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/bin/csh/USD.doc/csh.4 b/bin/csh/USD.doc/csh.4 new file mode 100644 index 0000000..ee862df --- /dev/null +++ b/bin/csh/USD.doc/csh.4 @@ -0,0 +1,178 @@ +.\" Copyright (c) 1980, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. All advertising materials mentioning features or use of this software +.\" must display the following acknowledgement: +.\" This product includes software developed by the University of +.\" California, Berkeley and its contributors. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)csh.4 8.1 (Berkeley) 6/8/93 +.\" +.nr H1 3 +.NH +Other, less commonly used, shell features +.NH 2 +Loops at the terminal; variables as vectors +.PP +It is occasionally useful to use the +.I foreach +control structure at the terminal to aid in performing a number +of similar commands. +For instance, there were at one point three shells in use on the Cory \s-2UNIX\s0 +system at Cory Hall, +`/bin/sh', +`/bin/nsh', +and +`/bin/csh'. +To count the number of persons using each shell one could have issued +the commands +.DS +% grep \-c csh$ /etc/passwd +27 +% grep \-c nsh$ /etc/passwd +128 +% grep \-c \-v sh$ /etc/passwd +430 +% +.DE +Since these commands are very similar we can use +.I foreach +to do this more easily. +.DS +% foreach i (\'sh$\' \'csh$\' \'\-v sh$\') +? grep \-c $i /etc/passwd +? end +27 +128 +430 +% +.DE +Note here that the shell prompts for +input with `? ' when reading the body of the loop. +.PP +Very useful with loops are variables which contain lists of filenames +or other words. +You can, for example, do +.DS +% set a=(\`ls\`) +% echo $a +csh.n csh.rm +% ls +csh.n +csh.rm +% echo $#a +2 +% +.DE +The +.I set +command here gave the variable +.I a +a list of all the filenames in the current directory as value. +We can then iterate over these names to perform any chosen function. +.PP +The output of a command within `\`' characters is converted by +the shell to a list of words. +You can also place the `\`' quoted string within `"' characters +to take each (non-empty) line as a component of the variable; +preventing the lines from being split into words at blanks and tabs. +A modifier `:x' exists which can be used later to expand each component +of the variable into another variable splitting it into separate words +at embedded blanks and tabs. +.NH 2 +Braces { ... } in argument expansion +.PP +Another form of filename expansion, alluded +to before involves the characters `{' and `}'. +These characters specify that the contained strings, separated by `,' +are to be consecutively substituted into the containing characters +and the results expanded left to right. +Thus +.DS +A{str1,str2,...strn}B +.DE +expands to +.DS +Astr1B Astr2B ... AstrnB +.DE +This expansion occurs before the other filename expansions, and may +be applied recursively (i.e. nested). +The results of each expanded string are sorted separately, left +to right order being preserved. +The resulting filenames are not required to exist if no other expansion +mechanisms are used. +This means that this mechanism can be used to generate arguments which are +not filenames, but which have common parts. +.PP +A typical use of this would be +.DS +mkdir ~/{hdrs,retrofit,csh} +.DE +to make subdirectories `hdrs', `retrofit' and `csh' +in your home directory. +This mechanism is most useful when the common prefix is longer +than in this example, i.e. +.DS +chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}} +.DE +.NH 2 +Command substitution +.PP +A command enclosed in `\`' characters is replaced, just before +filenames are expanded, by the output from that command. +Thus it is possible to do +.DS +set pwd=\`pwd\` +.DE +to save the current directory in the variable +.I pwd +or to do +.DS +ex \`grep \-l TRACE *.c\` +.DE +to run the editor +.I ex +supplying as arguments those files whose names end in `.c' +which have the string `TRACE' in them.* +.FS +*Command expansion also occurs in input redirected with `<<' +and within `"' quotations. +Refer to the shell manual section for full details. +.FE +.NH 2 +Other details not covered here +.PP +In particular circumstances it may be necessary to know the exact +nature and order of different substitutions performed by the shell. +The exact meaning of certain combinations of quotations is also +occasionally important. +These are detailed fully in its manual section. +.PP +The shell has a number of command line option flags mostly of use +in writing \s-2UNIX\s0 programs, +and debugging shell scripts. +See the csh(1) manual section for a list of these options. +.bp |