cal -This command will print a calendar for a specified month and/or year.
To show this month's calendar, enter:cal
To show a twelve-month calendar for 2008, enter:
cal 2008
To show a calendar for just the month of June 1970, enter:
cal 6 1970
cat -This command outputs the contents of a text file. You can use it to read brief files or to concatenate files together.
To appendfile1 onto the end of file2,
enter:cat file1 >> file2
To view the contents of a file named
myfile,
enter:cat myfile
Because
cat displays text without pausing, its output
may quickly scroll off your screen. Use the less command (described below) or an
editor for reading longer text files.cd -This command changes your current directory location. By default, your Unix login session begins in your home directory.
To switch to a subdirectory (of the current directory) namedmyfiles, enter:cd myfiles
To switch to a directory named
/home/dvader/empire_docs, enter:cd /home/dvader/empire_docs
To move to the parent directory of the current directory, enter:
cd ..
To move to the root directory, enter:
cd /
To return to your home directory, enter:
cd
chmod -This command changes the permission information associated with a file.
Every file (including directories, which Unix treats as files) on a Unix system is stored with records indicating who has permission to read, write, or execute the file, abbreviated as r, w, and x.
These permissions are broken down for three categories of user: first, the owner of the file; second, a group with which both the user and the file may be associated; and third, all other users.
These categories are abbreviated as u for owner (or user), g for group, and o for other.
To allow yourself to execute a file that you own namedmyfile, enter:
chmod u+x myfile
To allow anyone who has access to the directory in which
myfile is stored to read or execute
myfile, enter:chmod o+rx myfile
You can view the permission settings of a file using the
ls command, described below.
Note: Be careful with the
chmod command.
If you tamper with the directory permissions of your home directory,
for example, you could lock yourself out or allow others unrestricted
access to your account and its contents.For more, see In Unix, how do I change the permissions for a file?
cp -This command copies a file, preserving the original and creating an
identical copy. If you already have a file with the new name,
cp will overwrite and destroy the duplicate. For this
reason, it's safest to always add -i after the
cp command, to force the system to ask for your approval
before it destroys any files.
The general syntax for cp
is:
cp -i oldfile newfile
To copy a file named
meeting1 in the directory
/home/dvader/notes to your current directory,
enter:cp -i /home/dvader/notes/meeting1 .
The
. (period) indicates the current
directory as destination, and the -i ensures
that if there is another file named meeting1 in the current
directory, you will not overwrite it by accident.
To copy a file named
oldfile in the current directory to
the new name newfile in the mystuff
subdirectory of your home directory, enter:cp -i oldfile ~/mystuff/newfile
The
~ character (tilde) is interpreted as
the path of your home directory.
Note: You must have permission to read a file in order to copy it.
date -The date command displays the current day, date, time,
and year.
To see this information, enter:date
df -This command reports file system disk usage (i.e., the amount of space taken up on mounted file systems).
For each mounted file system,
df reports the file system device, the number of
blocks used, the number of blocks available, and the
directory where the file system is mounted.
To find out how much disk space is used on each file system, enter the
following command:
df
If the
df command is not configured to show blocks in
kilobytes by default, you can issue the following command:
df -k
du -This command reports disk usage (i.e., the amount of space taken up by a group of files).
The du command descends all
subdirectories from the directory in which you enter the command,
reporting the size of their contents, and finally reporting a total
size for all the files it finds.
To find out how much disk space your files take up, switch to your
home directory with the cd command, and
enter:
du
The numbers reported are the sizes of the files; on different systems, these sizes will be in units of either 512 byte blocks or kilobytes. To learn which is the case, use the
man command, described below. On most
systems, du -k will give sizes in kilobytes.
find -The find command lists all of the files within a
directory and its subdirectories that match a set of conditions. This
command is most commonly used to find all of the files that have a
certain name.
To find all of the files named myfile.txt in your current
directory and all of its subdirectories, enter:
find . -name myfile.txt -print
To look in your current directory and its subdirectories for all of the files that end in the extension
.txt , enter:
find . -name "*.txt" -print
In these examples, the
. (period) represents
your current directory. It can be replaced by the full pathname of
another directory to search. For instance, to search for files named
myfile.txt in the directory
/home/user/myusername and its subdirectories, enter:
find /home/user/myusername/ -name myfile.txt -print On some systems, omitting the final
/ (slash)
after the directory name can cause find to fail to return
any results.
As a shortcut for searching in your home directory, enter:
find "$HOME/" -name myfile.txt -print
jobs -This command reports any programs that you suspended and still have
running or waiting in the background (if you had pressed
Ctrl-z to suspend an editing session, for
example).
For a list of suspended jobs, enter:
jobsEach job will be listed with a number; to resume a job, enter
% (percent sign) followed by the number of
the job. To restart job number two, for example, enter:%2
This command is only available in the
csh,
bash, tcsh, and ksh shells.kill -Use this command as a last resort to destroy any jobs or programs that you suspended and are unable to restart. Use the jobs command to see a list of suspended jobs.
To kill suspended job number three, for example, enter:
kill %3Now check the
jobs command again. If the job has not
been cancelled, harsher measures may be necessary. Enter:
kill -9 %3
less and more -Both less and more display the contents of a
file one screen at a time, waiting for you to press the Spacebar
between screens.
This lets you read text without it scrolling quickly
off your screen. The less utility is generally more
flexible and powerful than more, but more is
available on all Unix systems while less may not be.
To read the contents of a file named textfile in the
current directory, enter:
less textfile
The
less utility is often used for reading the output
of other commands. For example, to read the output of the
ls command one screen at a time, enter:
ls -la | less
In both examples, you could substitute
more for
less with similar results. To exit either
less or more, press q .
To exit less after viewing the file, press
q .
Note: Do not use
less or
more with executables (binary files), such as
output files produced by compilers. Doing so will display garbage and
may lock up your terminal.
lpr and lp -These commands print a file on a printer connected to the computer network.
The lpr command is used on BSD
systems, and the lp command is used in System
V. Both commands may be used on the
UITS systems.
To print a file named myfile on a printer named
lp1 with lpr, enter:
lpr -Plp1 myfile
To print the same file to the same printer with
lp, enter:
lp -dlp1 myfile
Note: Do not print to a printer whose name or location is unfamiliar to you.
ls -This command will list the files stored in a directory.
To see a brief, multi-column list of the files in the current directory, enter:
lsTo also see "dot" files (configuration files that begin with a period, such as
.login ), enter:
ls -a
To see the file permissions, owners, and sizes of all files, enter:
ls -la
If the listing is long and scrolls off your screen before you can read it, combine
ls with the less utility, forexample:
ls -la | less
man -This command displays the manual page for a particular command.
If
you are unsure how to use a command or want to find out all its
options, you might want to try using man to view the manual
page.
For example, to learn more about the ls command, enter:
man ls
To learn more about
man, enter:
man man
If you are not sure of the exact command name, you can use
man with the -k option to help
you find the command you need. To see one line summaries of each
reference page that contains the keyword you specify, enter:
man -k keyword
Replace
keyword in the above example with the keyword
which you want to reference. Also see
mkdir
This command will make a new subdirectory.To create a subdirectory named
mystuff in the current
directory, enter:
mkdir mystuff
To create a subdirectory named
morestuff in the existing
directory named /tmp, enter:
mkdir /tmp/morestuff
Note: To make a subdirectory in a particular directory, you must have permission to write to that directory.
mv -This command will move a file. You can use mv not only
to change the directory location of a file, but also to rename files.
Unlike the cp command, mv will not preserve
the original file.
Note: As with the cp command, you should
always use -i to make sure you do not overwrite an
existing file.
To rename a file named
oldname in the current directory
to the new name newname, enter:
mv -i oldname newname
To move a file named
hw1 from a subdirectory named
newhw to another subdirectory named oldhw
(both subdirectories of the current directory), enter:
mv -i newhw/hw1 oldhw
If, in this last operation, you also wanted to give the file a new name, such as
firsthw, you would enter:
mv -i newhw/hw1 oldhw/firsthw
ps -The ps command displays information about programs (i.e.,
processes) that are currently running. Entered without arguments, it
lists basic information about interactive processes you own. However,
it also has many options for determining what processes to display, as
well as the amount of information about each. Like lp
and lpr, the options available differ between BSD and
System V implementations. For example, to view detailed information
about all running processes, in a BSD system, you would use
ps with the following arguments:
ps -alxww
To display similar information in System V, use the arguments:
ps -elf
pwd
This command reports the current directory path. Enter the command by itself:pwd
rm
This command will remove (destroy) a file. You should enter this command with the -i option, so that you'll be
asked to confirm each file deletion. To remove a file named
junk, enter:
rm -i junk
Note: Using
rm will remove a file
permanently, so be sure you really want to delete a file before you
use rm.
To remove a non-empty subdirectory,
rm accepts the
-r option. On most systems this will prompt you
to confirm the removal of each file. This behavior can be prevented by
adding the -f option. To remove an entire
subdirectory named oldstuff and all of its contents,
enter:
rm -rf oldstuff
Note: Using this command will cause
rm
to descend into each subdirectory within the specified subdirectory
and remove all files without prompting you. Use this command with
caution, as it is very easy to accidently delete important files. As a
precaution, use the ls command to list the files within
the subdirectory you wish to remove. To browse through a subdirectory
named oldstuff, enter:
ls -R oldstuff | less
rmdir
This command will remove a subdirectory. To remove a subdirectory namedoldstuff, enter:
rmdir oldstuff
Note: The directory you specify for removal must be empty. To clean it out, switch to the directory and use the
ls and rm commands to inspect and delete
files.
set
This command displays or changes various settings and options associated with your Unix session.To see the status of all settings, enter the command without options:
set
If the output scrolls off your screen, combine
set with
less:
set | less
The syntax used for changing settings is different for the various kinds of Unix shells; see the
man
entries for set and the references listed at the end of
this document for more information.
vi
This command starts the vi text editor. To edit a file namedmyfile in the current directory, enter:
vi myfile
The vi editor works fairly differently from other text editors.
The very least you need to know to start using vi is that in order to enter text, you need to switch the program from command mode to insert mode by pressing
i .To navigate around the document with the cursor keys, you must switch back to command mode by pressing
Esc.To execute any of the following commands, you must switch from command mode to ex mode by pressing
: (the colon key): Enter
w to save; wq to
save and quit; q! to quit without saving.
w and who
Thew and who commands are similar programs
that list all users logged into the computer. If you use
w, you also get a list of what they are doing. If you use
who, you also get the IP numbers or computer
names of the terminals they are using.