Utilities

Understand and try all of those in chapter 3 which we do not cover in class, they will be tested on as well as the more complicated ones presented in this lecture.

date

displays the current date and time

cal

displays a calendar

0 arguments

current month and year

1 argument

assumed to be a year

2 arguments

allow you to specify month and year

man

the manual display command
more details
the manual is not only to tell you how to use the different shell commands

% man passwd

and to tell you which shell commands correspond to a given keyword as in: % man -k password or
% apropos password

or a short summary: % man -f passwd
% whatis passwd

whereis and which

help you find locations of files corresponding to commands commands are just names of executable files search path shell variable named $path or $PATH

echo

allows you to see the contents of a shell variable % echo $path

search path tells it to look in each of the places listed, in the order listed to find the directions for what to do on the command named.

ONLY COMMANDS will not search for filenames given as arguments !!!

grep

"global regular expression print"
format:
% grep string filelist,
% grep man this.file
% grep man *

regular expression means there is a different set of "wildcards"
^   beginning of line
$   end of line
\< and \>   beginning and ending of a word - not on OSF
.   replaced by any 1 character
[ ] choose one from the class of characters listed (just like the shell level wildcard)
*   multiplies the character before it to 0 or more times
" "   quotes a string

% grep Jan friend.list
% grep \<Jan\> friend.list
% grep [abc].1 this.list
a.1 b.1 c.1 ax1 b31 etc.
% grep [abc]*.1 this.list
a.1 b.1 c.1 aa.1 ab.1 ba.1 abx1 abb31 etc.

tar

"tape archive"
allows you to collect a group of named files into one file so that the group is named one thing for doing things like transferring to another machine as a group or storing.

% tar -cvf all.file file1 file2 file3 file4
-c stands for create
-f stands for file (and must be the last option on some systems)
-v stands for verbose

% tar -xvf all.file
-x stands for extract

who am i

to find the login id and machine name of the current login session

whoami

to find the login id of the current login session

hostname

tells just the name of the machine and its address

From text:

cat, head, tail	display contents of a text file
compress, uncompress, zcat	deal with compressing, uncompressing and seeing contents of compressed files
file	guesses at the type of the file named
sed	non-interactive editor
diff	compares two files
sort	orders the lines of a file
uniq	removes sequential duplicate lines from a file