Features of the TCSH Shell

LG #35
Patterns

Many operations in the shell work on many files, e.g., all files ending with .tex or starting with test-. TCSH has the ability to type all these files for you, with file patterns. The following list shows which possibilities exist:

*

Match any number of characters

?

Match a single character

[...]

Match any single character in the list

[x-y]

Match any character within the range of characters from x to y

[^...]

Match elements which do not match the list

{...}

This expands to all the words listed. There's no need that they match

^...

^ in the beginning of a pattern negates the pattern

Examples
  • *.tex: match all files ending with .tex

  • ^*.tex: match all files which does not end with .tex

  • xxx{ab,cde,hifj}yy: match xxxabyy xxxcdeyy and xxxhifjyy

  • *.[ch] or *.{c,h}: match all .c and .h files

The Shell Expand Patterns

An important thing to be aware of is that it is the shell which expands the patterns, and not the program, which is executed with the pattern.

An example of this is the program mcopy which copies files from disk. To copy all files, you may wish to use a asterisk, as in: mcopy a:* /tmp. However, this does not work, since the shell will try to expand the asterisk. Since it cannot find any files which start with a:, it will signal an error. So if you wish to send a asterisk to the program, you have to escape the asterisk: mcopy a:\* .

There are two very useful key bindings which can be used with patterns. The first is C-xg, which lists all the files matching the pattern, without executing the command. The other is C-x*, which expands the asterisk on the command line. This is especially useful if you wish to delete all files ending in .c except important.c, stable.c and another.c. Creating a pattern for this might be very hard, so just use the pattern *.c. Then type C-x*, which will expand *.c to all your .c files. Now it's easy to remove the three files from the list.

Aliases

When using the shell, you will soon recognize that certain commands are typed again and again. One of the top ten is surely ls -la, which lists all files in a directory in long form.

TCSH has a mechanism to create aliases for commands. This means that you can create an alias for ls -la called la.

Aliases may refer to the arguments of the command line. This means that you can create a command called pack which takes a directory name and packs the directory with tar and gz.

Aliases can be a bit hard to create since you often want history/variable references expanded at the time of use, not at the definition time. This can be done more easily with TDG; go to the page aliases to define aliases. If you end up with an alias you cannot define on this page, but you can in TCSH, please send me e-mail (blackie@imada.ou.dk). For more information about aliases, see the TCSH manual at http://www.imada.ou.dk/Technical/Manpages/tcsh/Alias_substitution.html.

Timing Programs

Have you ever needed to know how long a program took to run, i.e., how much CPU it used? If so, you may recognize the output from the TCSH built-in time command:

0.020u 0.040s 0:00.11 54.5%     0+0k 0+0io 21pf+0w

Informative? Yes but... the GNU time command is a bit more understandable:

0.01user 0.08system 0:00.32elapsed 28%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+0minor)pagefaults 0swaps
In TDG you can configure the output from the time command on the page called jobs shown in Figure 5.

Figure 5. TDG Jobs Page

References

As you may have guessed, TDG and this article will help you a lot in the use of TCSH, but you may need to read a bit more to get even more out of TCSH. Here are a few references:

  • The TCSH manual page at http://www.imada.ou.dk/Technical/Manpages/tcsh/top.html

  • Using csh & tcsh by Paul DuBois, published by O'Reilly & Associates, 1995: http://www.primate.wisc.edu/software/csh-tcsh-book/

  • The TCSH mailing list at tcsh@mx.gw.comr (to join send mail to listserv@mx.gw.com with body text SUBscribe TCSH your name)

Jesper Pedersen lives in Odense, Denmark, where he has studied computer science at Odense University since 1990. He is a system manager at the university and also teaches computer science. He is very proud of his “child”, The Dotfile Generator, which he wrote as part of his job at the university. In his spare time, he does Jiu-Jitsu, listens to music, drinks beer and has fun with his girlfriend. He loves pets, and has a 200 litre aquarium and two very cute rabbits. His home page can be found at http://www.imada.ou.dk/~blackie/“, and he can be reached at blackie@imada.ou.dk. This article first appeared in Issue 12 of Linux Gazette.

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