Sams Teach Yourself Linux in 24 Hours:Reading and Navigation Commands:EarthWeb Inc.-
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Page 50
do. But what if you want to do something and can't remember which program does
what? In this case, you can turn to the apropos command.
For example, if you can't remember which command searches for files, you can enter
# apropos search
apropos (1) - search the whatis database for strings
badblocks (8) - search a device for bad blocks
bsearch (3) - binary search of a sorted array.
conflict (8) - search for alias/password conflicts
find (1) - search for files in a directory hierarchy
hcreate, hdestroy, hsearch (3) - hash table management
lfind, lsearch (3) - linear search of an array.
lkbib (1) - search bibliographic databases
lookbib (1) - search bibliographic databases
lsearch (n) - See if a list contains a particular element
manpath (1) - determine user's search path for man pages
strpbrk (3) - search a string for any of a set of characters
strspn, strcspn (3) - search a string for a set of characters
tsearch, tfind, tdelete, twalk (3) - manage a binary tree
whatis (1) - search the whatis database for complete words.
zgrep (1) - search possibly compressed files for a regular expression
zipgrep (1) - search possibly zip files for a regular expression
You'll see a list of programs from the whatis database on your screen.
The apropos command uses this database to search for the keyword you entered. If you keep your manual
pages and whatis database up-to-date, you'll be able to use
apropos to help you find the program you need.
JUST A MINUTE
You can also use the man command's -K option to do the same thing as
apropos, but the search will be slow, and you'll be presented each manual page in
the search result. For example, to search for any programs dealing with
PostScript, you can try
# man -K PostScript
This can result in the following output (before you quit with q):
/usr/dt/man/man5/DtStdAppFontNames.5? [ynq] n
/usr/dt/man/man4/dtdtsfile.4? [ynq] n
/usr/man/man7/unicode.7? [ynq] n
/usr/man/man7/suffixes.7? [ynq] n
/usr/man/man7/groff_char.7? [ynq] n
/usr/man/man1/convert.1x? [ynq] n
/usr/man/man1/xv.1? [ynq] n
/usr/man/man1/xdvi.1? [ynq] n
/usr/man/man1/dvips.1? [ynq] n
/usr/man/man1/afm2tfm.1? [ynq] n
/usr/man/man1/ps2pk.1? [ynq] n
/usr/man/man1/ps2frag.1? [ynq] q
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Reading Directories and Files
Now that you know about directory navigation, searching for files, or how to find
more information about programs, I'll introduce you to other basic Linux commands you
can use. This section shows you how to list the contents of directories, make a catalog of
your hard drive, and read the contents of files. You'll learn the basic forms of these
commands to help get you started.
Listing Directories with the ls Command
The ls (list directory) command will quickly become one of your most often used
programs. In its simplest form, ls lists nearly all of the files in the current directory. But this
command, which has such a short name, probably has more command-line options (more than 75
at last count) than any other program!
In the simple form, ls lists your files:
# ls
News axhome nsmail search
author.msg documents reading vultures.msg
auto mail research
You can also list the files as a single line, with comma separations, with the
-m option:
# ls -m
News, author.msg, auto, axhome, documents, mail, nsmail, reading,
 research, search, vultures.msg
If you don't like this type of listing, you can have your files sorted horizontally, instead
of vertically (the default), with the -x option:
# ls -x
News axhome nsmail search
author.msg documents reading vultures.msg
auto mail research
But are all these just files, or are there several directories? One way to find out is to
use the -F option:
# ls -F
News/ axhome/ nsmail/ search*
author.msg documents/ reading/ vultures.msg
auto/ mail/ research/
As you can see, the -F option causes the ls command to show the directories, each with
a / character appended to the filename. The asterisk
(*) shows that the file search is an executable program. But are these all the files in this directory? If you want to see
everything, you can use the -a option with -F, as follows:
# ls -aF
./ .dt/ .neditdb auto/
../ .dtprofile* .netscape/ axhome/
Page 52
.Xauthority .festival_history .newsrc documents/
.Xdefaults .forward .oldnewsrc mail/
.addressbook .fvwm2rc95* .pinerc nsmail/
.addressbook.lu .index/ .procmail/ reading/
.bash_history .mailcap .procmailrc research/
.bash_logout .mailrc .tin/ search*
.bash_profile .mime.types .xinitrc* vultures.msg
.bashrc .ncftp/ News/
.desksetdefaults .nedit author.msg
Using the -F option is one way to see the files and directories in your listings, but if
you have a color monitor, or use X11 in color, you can tell
ls to show files, directories, or executable files in different colors. To do this, use the
--color option. In X11, using the rxvt terminal, directories will be blue, programs will be green, and regular files will be
black. You can also customize which colors are used for different types of files.
Look in the /etc/ directory for the file named
DIR_COLORS. Copy this file, renaming it to
.dir_colors, and save it in your home directory. You can then edit this file to customize or
add file types recognized for colorizing. See the
DIR_COLORS file for details.
Long Directory Listing
Would you like even more information about your files? You can view the long
format listing by using the ls -l option, for example:
# ls -l
drwxr-xr-x 2 bball bball 1024 Nov 12 08:20 News
-rw-rw-r-- 1 bball bball 4766 Nov 12 07:41 author.msg
drwxrwxr-x 2 bball bball 1024 Nov 5 10:04 auto
drwxrwxr-x 3 bball bball 1024 Nov 12 13:54 axhome
drwxrwxr-x 2 bball bball 1024 Nov 12 14:33 documents
drwx------ 2 bball bball 1024 Nov 12 14:02 mail
drwx------ 2 bball bball 1024 Sep 15 01:57 nsmail
drwxrwxr-x 2 bball bball 1024 Oct 29 20:28 reading
drwxrwxr-x 5 bball bball 1024 Nov 5 10:03 research
-rwxrwxr-x 1 bball bball 200 Oct 24 13:24 search
-rw-rw-r-- 1 bball bball 801 Nov 11 22:46 vultures.msg
As you can see, there are eight different columns. The first column is the file's
permissions flags, which are covered in Hour 21, "Handling Files." These flags generally show the
file's type, and who can read, write (or modify or delete), or run the file. The next column
shows the number of links, which are discussed in Hour 5, "Manipulation and
Searching Commands." Next is the owner name, followed by group name. Owners and groups
are discussed in Hour 21. The file size is listed next, followed by a timestamp of the file
or directory was created or last modified. The last column, obviously, is each file's name.
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