Learning the Command Line
Lynn David Newton
plug-discuss@lists.plug.phoenix.az.us
Sun, 9 Feb 2003 19:08:46 -0700
m> Does 'man bash' list all of the commands? If not,
m> how do you get a list of all the commands?
There is no such thing as "all the commands". What you
have available as executable commands depends on what
is found by your PATH variable and what is installed on
your machine. This is at minimum a couple thousand
files. To get some idea, do this:
for i in $(echo $PATH | tr ":" " ")
do
ls $i
done
every word you see (with the exception of a few that
might be directories) is an executable command in your
path.
Change the last line of that sequence to
done | wc -w
to get a count, if you're curious. In my environment
the number is 4096.
In addition, there are a great many more commands that
are built right into your shell.
Most people would say that's a few too many commands to
get to know. They are right. You don't need to know
more than a small fraction of those, and more than you
need to know the half million or so words in the
English language in order to speak English well.
I will agree that the place to start is with the bash
manual (assuming that's your shell). It will teach you
not only the "words" (commands), but about the
"grammar", the basics of the Unix way of doing things,
with concepts about variables and parameters,
redirection, pipes, and all that good stuff.
Almost any standard reference you can find (many of
them free online) will list a common set of useful
commands of reasonable size.
In fact ... I have attached (inline) a short list that
I used as a handout to my classes in Linux/Unix at UAT
last year. Keep in mind that this is a list of the ones
*I* thought were important. Experts will disagree on
some of the marginal commands, but if you know all of
these, you will be able to go a long way:
-------------------------------------------------------
Unix Esperanto
--------------
The following is a list of commands that your instructor believes
should be in every Unix user's basic vocabulary. Included are some
commands that are not disk-based, but are internal to the shell.
This list was culled out of over 4000 executable commands found in
your instructor's PATH.
alias (n) - substitute name for a command
apropos (1) - search the whatis database for strings
basename (1) - strip directory and suffix from filenames
bash (1) - GNU Bourne-Again Shell
cal (1) - displays a calendar
case (n) - evaluate one of several choices
cat (1) - concatenate files and print on the standard output
cd (n) - Change working directory
chgrp (1) - change group ownership
chmod (1) - change file access permissions
chown (1) - change file owner and group
cksum (1) - checksum and count the bytes in a file
clear (1) - clear the terminal screen
cmp (1) - compare two files
cp (1) - copy files and directories
cut (1) - remove sections from each line of files
date (1) - print or set the system date and time
df (1) - report filesystem disk space usage
diff (1) - find differences between two files
dirname (1) - strip non-directory suffix from file name
du (1) - estimate file space usage
echo (1) - display a line of text
emacs (1) - GNU project Emacs
env (1) - run a program in a modified environment
eval (n) - evaluate string and numeric expressions
exec (n) - overlay current process
exit (n) - cause normal program termination
export (n) - make variables global in sub-shells
fc (n) - fix command by editing it
fg (n) - foreground
file (1) - determine file type
find (1) - search for files in a directory hierarchy
for (n) - for loop
ftp (1) - Internet file transfer program
gawk (1) - pattern scanning and processing language
gcc (1) - GNU project C and C++ Compiler (gcc - 2.96)
grep (1) - print lines matching a pattern
head (1) - output the first part of files
help (n) - bash builtin command help
history (n) - shell history
host (1) - DNS lookup utility
id (1) - print real and effective UIDs and GIDs
if (n) - execute scripts conditionally
info (1) - read Info documents
jobs (n) - shell job control
kill (1) - terminate a process
ksh (1) - Public domain Korn shell
ln (1) - make links between files
login (1) - sign on
lp (1) - send requests to an LPRng print service
lpq (1) - spool queue examination program
lpr (1) - off line print
ls (1) - list directory contents
man (1) - format and display the on-line manual pages
md5sum (1) - compute and check MD5 message digest
mkdir (1) - make directories
more (1) - file perusal filter for crt viewing
mv (1) - move (rename) files
nohup (1) - run a command immune to hangups
passwd (1) - update a user's authentication tokens(s)
popd (n) - pop current directory off stack
ps (1) - report process status
pushd (n) - push current directory on stack
pwd (1) - print name of current/working directory
read (n) - read a variable from stdin
return (n) - return from a function
rm (1) - remove files or directories
rmdir (1) - remove empty directories
sed (1) - a Stream EDitor
set (n) - display and set positional parameters
shift (n) - move positional parameters
sleep (1) - delay for a specified amount of time
sort (1) - sort lines of text files
ssh (1) - OpenSSH SSH client (remote login program)
sum (1) - checksum and count the blocks in a file
tail (1) - output the last part of files
tee (1) - read from stdin and write to stdout and files
telnet (1) - user interface to the TELNET protocol
test (1) - check file types and compare values
touch (1) - change file timestamps
tr (1) - translate or delete characters
type (n) - show pathnames of commands
typeset (n) - declare shell variables with attributes
ulimit (n) - get and set user limits
umask (n) - set file creation mask
unalias (n) - turn off alias(es)
uname (1) - print system information
uniq (1) - remove duplicate lines from a sorted file
unset (n) - delete variables
until (n) - execute until a condition is true
vim (1) - Vi IMproved, a programmers text editor
wait (n) - wait for process termination
wc (1) - print the number of bytes, words, lines in files
whatis (1) - search the whatis database for complete words
whereis (1) - locate binary, source, man page for command
which (1) - show full path of commands
while (n) - execute as long as condition is true
who (1) - show who is logged on
whoami (1) - print effective userid
whois (1) - query a whois or nicname database
xargs (1) - build and execute command lines from standard input
xterm (1x) - terminal emulator for X (graphical program)
--
Lynn David Newton
Phoenix, AZ