-
ls - lists files
ls - show contents of working directory
ls file - list file, if it exists in working directory
ls dir - show contents of the directory dir
ls -a - shows all your files, including hidden ones
ls -al - give detailed listing of contents
ls -F - mark directories with "/" and executable
files with "*"
ls *.doc - show all files with suffix ".doc"
-
more - browses/displays files one screen at a time. Use h for help,
spacebar to page, b for back, q to quit, /string to search for string
more sample.f
-
pg - browses/displays files one screen at a time. Similar to the
more utility in function but has different commands and options.
See the man page for details.
pg sample.f
-
less - similar to more, but with more features. Not available
on every system.
less sample.f
-
head - displays the first n lines of a file
head sample.f - display first 10 lines (default)
head -5 sample.f - display first 5 lines
head -25 sample.f - display first 25 lines
-
tail - displays the last n lines or n characters of a file
less sample.f - display last 10 lines (default)
less -5 sample.f - display last 5 lines
less -5c sample.f - display last 5 characters
less -25 sample.f - display last 25 lines
-
cat - dumps the entire file to the screen without paging. This
command is more useful for concatenating (hence the name "cat")
files together than it is for reading files.
cat myprog.c - diplays entire file
cat -b myprog.c - shows line numbers
cat file1 file2 > file3 - adds file1 and file2 to make
file3
-
cp - copies files. Will overwrite unless otherwise specified.
Must also have write permission in the destination directory.
cp sample.f sample2.f - copies sample.f to sample2.f
cp -R dir1 dir2 - copies contents of directory
dir1 to dir2
cp -i file.1 file.new - prompts if file.new will be
overwritten
cp *.txt chapt1 - copies all files with .txt
suffix to directory chapt1
cp /usr/doc/README ~ - copies file to your home
directory
cp ~betty/index . - copies the file "index" from
user betty's home directory
to current directory
-
mv - moves files. Will overwrite unless otherwise specified.
Must also have write permission in the destination directory.
mv sample.f sample2.f - moves sample.f to sample2.f
mv dir1 newdir/dir2 - moves contents of directory
dir1 to newdir/dir2
mv -i file.1 file.new - prompts if file.new will be
overwritten
mv *.txt chapt1 - moves all files with .txt
suffix to directory chapt1
-
rm - deletes/removes files or directories if file permissions
permit.
rm sample.f - deletes sample.f
rm chap?.txt - deletes all files with chap as the
first four characters of their name
and with .txt as the last four
characters of their name
rm -i * - deletes all files in current directory
but asks first for each file
rm -r /olddir - recursively removes all files in the
directory olddir, including the
directory itself
Begin the Filesystem
exercises - Part 1.
-
file - identifies the "type" of file. The command syntax is:
file filename
For example:
file * - reports all files in current
directory and their types. The
output might appear as shown below:
about.html: ascii text
bin: directory
staff.directory: English text
bggen: executable or object module not stripped
bmbinc: commands text
machines.sp1: [nt]roff, tbl, or eqn input text
man2html: executable or object module not stripped
man2html.c: ascii text
-
find - finds files. The syntax of this command is:
find pathname -name filename -print
The pathname defines the directory to start from. Each subdirectory of this
directory will be searched.
The -print option must be used to display results.
You can define the filename using wildcards. If these are used, the
filename must be placed in 'quotes'.
find . -name mtg_jan92 -print - looks for the file
mtg_jan92 in current
directory
find ~/ -name README -print - looks for files called
README throughout your
home directory
find . -name '*.fm' -print - looks for all files with
.fm suffix in current
directory
find /usr/local -name gnu -type d -print
- looks for a directory
called gnu within the
/usr/local directory
-
diff - comparing two files or directories. Indicates which lines
need be added (a), deleted (d) or changed (c). Lines in file1 are
identified with a (<) symbol: lines in file2 with a (>) symbol
diff file1 file2 - compares file1 to file2
diff -iw file1 file2 - compares two files ignoring
letter case and spaces
diff dir1 dir2 - compares two directories
showing files which are
unique to each and also,
line by line differences
between any files in common.
For example, if file1 and file2 are:
John erpl08@ed John erpl08@ed
Joe CZT@cern.ch Joe CZT@cern.ch
Kim ks@x.co Jean JRS@pollux.ucs.co
Keith keith@festival Jim jim@frolix8
Kim ks@x.co
Keith keith@festival
Using the diff command: diff file1 file2
Yields the output:
2a3,4
> Jean JRS@pollux.ucs.co
> Jim jim@frolix8
Which means that to make these files match you need to add (a)
lines 3 and 4 (3,4) of file2 (>) after line 2 in file1.
-
sdiff - similar to diff, but displays each line of the two files
side by side, making it easier for you to see the differences between them
Lines that are different are shown with a | symbol. Lines unique to
file1 are identified by a < symbol; lines unique to file2 with
a > symbol. Identical lines appear next to each other.
The option -w 80 is used to set the width of the output from the command
to 80 characters. The default is 130 characters.
sdiff -w 80 file1 file2
Mike erpl08@ed | John erpl08@ed
Joe CZT@cern.ch Joe CZT@cern.ch
> Jean JRS@pollux.ucs.co
> Jim jim@frolix8
Kim ks@x.co Kim ks@x.co
Sam s.wally@aston <
Keith keith@festival Keith keith@festival
-
ln - link one file name to another. The command syntax is:
ln source linkname
Making a link to a file or directory does not create another copy of it.
It simply makes a connection between the source and the linkname. Allows
a single file to be "pointed to" by other filenames without having to
duplicate the file.
ln results.1 last.run - links filename "last.run" to
the real file results.1 in
the current directory.
ln notes ../Notes.jan - links filename "notes" in
current directory to real file
Notes.jan in parent directory.
-
sort - sorts files, merges files that are already sorted,
and checks files to determine if they have been sorted. The command
syntax is:
sort options filename
By default, lines in "filename" are sorted and displayed to the screen.
If the "filename" parameter specifies more than one file, the sort command
concatenates the files and sorts them as one file.
An output file can be specified with the -o flag.
Files can be sorted by "fields" - single or multiple.
The sort command supports many options. See the man page for details.
sort addresses - sorts the file
addresses and displays
output on screen
sort -o sorted addresses - sorts the file
addresses and writes
output to the file
called sorted.
sort -u -o mail_labels addresses - removes all duplicate
lines from the file
addresses and writes
the output in the
file mail_labels.
sort +2 -4 addresses - sorts the file by
its third and fourth
fields. Note that
+2 means to skip first
two fields and -4
means to stop after
the fourth field.
Continue the Filesystem
exercises - Part 2.
-
pwd - print working directory. Tells you which directory you
are currently in.
pwd
-
mkdir - make directory. Will create the new directory in your
working directory by default.
mkdir /u/training/data
mkdir data2
-
cd - change to specified directory. May specify either the
absolute or relative pathname. cd with no pathname changes to your home
directory.
cd /usr/local - change to /usr/local
cd doc/training - change to doc/training in current
directory
cd .. - change to parent directory
cd ~/data - change to data directory in
home directory
cd ~joe - change to user joe's home directory
cd - change to home directory
-
rmdir - remove directory. Directories must be empty before you
remove them.
rmdir project1
To recursively remove nested directories, use the rm command with the
-r option:
rm -r dirctory_name
Continue the Filesystem
exercises - Part 3.
- A summary of commands and utilities related to the UNIX file
system appears below. See the corresponding man pages for detailed
information.
awk -search for and process patterns in a file,
cat -display, or join, files
cd -change working directory
chgrp -change the group that is associated with a file
chmod -change the access mode of a file
chown -change the owner of a file
comm -compare sorted files
cp -copy files
df -display the amount of available disk space
diff -display the differences between two files
du -display information on disk usage
file -display file classification
find -find files
fsck -check and repair a file system
grep -search for a pattern in files
head -display the first few lines of a file
ln -create a link to a file
lp -print files (System V)
lpr -print files (Berkeley)
ls -list information about files
mkdir -create a directory
more -display a file one screen at a time (System V)
mv -move and/or rename a file
od -dump a file
pg -display a file one screen at a time (Berkeley)
pr -paginate a file
pwd -print the working directory
rm -remove (delete) files
rmdir -remove (delete) a directory
sed -stream editor (non-interactive)
sort -sort and/or merge files
spell -check a file for spelling errors
tail -display the last few lines of a file
tar -store or retrieve files from an archive file
umask -set file creation permissions
uniq -display the lines in a file that are unique
wc -counts lines, words and characters in a file
whatis -list man page entries for a command
whereis -show where executable is located in path
which -locate an executable program using "path"
- UNIX is a multi-user system. Every file and directory in your account can
be protected from or made accessible to other
users by changing its access permissions. Every user has responsibility
for controlling access to their files.
- Permissions for a file or directory may be any or all of:
r - read
w - write
x - execute = running a program
- Each permission (rwx) can be controlled at three levels:
u - user = yourself
g - group = can be people in the same project
o - other = everyone on the system
- File access permissions are displayed using the ls -l command.
The output from the ls -l command shows all permissions for all
levels as three groups of three according to the scheme:
owner read (r)
owner write (w)
owner execute (x)
group read (r)
group write (w)
group execute (x)
public read (r)
public write (w)
public execute (x)
which are displayed as: -rwxrwxrwx
Example outputs from the ls -l command:
-rw------- 2 smith staff 3287 Apr 8 12:10 file1
- User has read and write permission. Group and
others have no permissions.
-rw-r--r-- 2 smith staff 13297 Apr 8 12:11 file2
- User has read and write permission. Group and
others can only read the file.
-rwxr-xr-x 2 smith staff 4133 Apr 8 12:10 myprog
- User has read, write and execute permission.
Group and others can read and execute the file.
drwxr-x--- 2 smith staff 1024 Jun 17 10:00 SCCS
- This is a directory. The user has read, write and
execute permission. Group has read and execute
permission on the directory. Nobody else can
access it.
- Note: a directory must have both r and x permissions if the files it
contains are to be accessed.
- The chmod command is used to change access
permissions for files which you own. The syntax is:
chmod permission_triads filename
[who][action][permissions]
where:
who action permissions
u = user + = add r = read
g = group - = remove w = write
o = other x = execute
a = all
Examples:
chmod a+r sample.f
- Adds read permission for all users to the file
sample.f.
chmod o-r sample.f
- Removes read permission for others to the file
sample.f.
chmod og+rx prog*
- Adds read and execute permissions for group and
others to all files which contain "prog" as the
first four characters of their name.
chmod +w *
- Adds write permission for user to all files in
current directory.
- File access permissions can also be changed by a numerical (octal) chmod
specification. Read permission is given the value 4, write permission
the value 2 and execute permission 1.
r w x
4 2 1
These values are added together for any one user category:
0 = no permissions
1 = execute only
2 = write only
3 = write and execute (1+2)
4 = read only
5 = read and execute (4+1)
6 = read and write (4+2)
7 = read and write and execute (4+2+1)
So access permissions can be expressed as three digits. For example:
user group others
chmod 640 file1 rw- r-- ---
chmod 754 file1 rwx r-x r--
chmod 664 file1 rw- rw- r--
- Never set write permission for all other users on a file or directory
which is in your home directory. If you do other users will be able
to change its content. This can represent a serious security risk.
- The umask command is used to set your
default file permissions.
Typically, the umask command is included as part of your .profile, .cshrc
or .login file.
The umask command accepts only octal specifications. Note that these
are different than those used by the chmod command, and in fact,
represent which permissions to "mask out", or remove.
Octal number Access permissions given
0 rwx read, write and
execute
1 rw- read and write
2 r-x read and execute
3 r-- read only
4 -wx write and execute
5 -w- write only
6 --x execute only
7 --- no permissions
Example umask commands:
umask 077
- Subtracts 077 from the system defaults for files
(666) and directories (777). Results in default
access permissions for your files of 600
(rw-------) and for directories of 700
(rwx------).
umask 002
- Subtracts 002 from the sytem defaults to give a
default access permission for your files of 664
(rw-rw-r--) and for your directories of 775
(rwxrwxr-x).
umask 022
- Subtracts 022 from the system defaults to give a
default access permission for your files of 644
(rw-r--r--) and for your directories of 755
(rwxr-xr-x).
-
Begin the Access Permissions Exercise
