agenda basic unix commands (chapters 2 & 3) miscellaneous commands: which, passwd, date, ps /...

Agenda Basic Unix Commands (Chapters 2 & 3)

Miscellaneous Commands: which, passwd, date, ps / kill

Working with Files: file, touch, cat, more, less, grep,

head, tail, cp, mv, ls sort, diff

Communicating with Users who, finger

Textbook Coverage These slides are based on

Chapters 2 and 3 of “A Practical Guide to Linux”

Read pages 36 to 38, 41 to 46, and 49-57

Miscellaneous Commands

which passwd date ps / kill

which which is a utility that lists only the

directory path of the command that the shell will run when the user issues the command from the shell prompt.

For Example: which cp

passwd A user can change their account

password by issuing passwd command at shell prompt. The user will be prompted for their current password and then be prompted for new password and confirmation.

date The date command is used to display

the current date and time.

Example: date

Note: If you have superuser or "root" access, you can change the computer system's date and time.

ps / kill As mentioned in last week’s notes, the Unix OS

continually runs processes (jobs). The ps command is used to provide status information regarding the user’s processes, such as PID (process I.D. number). The kill command can be used to terminate process number (eg. kill [PID] or kill –9 [PID])

Options (for ps command):

-l Provides detailed process status info (eg parent PID)-a Provides process status info for all processes

-al Provides detailed info for all processes

Working with Files file, touch, cat, more, less grep, head, tail cp, mv, ls sort, diff

file The file command is used to identify a

type of file (for example, whether the file is an ASCII (text), executable file, graphics file, MS-PowerPoint file, a directory file, etc...). This command is useful if file does not contain an extension and therefore is hard to identify.

Example: file try_me (Identifies the file type of "try_me")

touch The touch command is used to create empty

files. This command is useful to create empty files to be edited later with content. Another use for this command is to create empty files in order to practise using Unix commands that may require a filename such as ls, cp, mv, etc…

Example: touch file1 file2 file3

(Creates 3 files in current directory)

cat The cat command is used to combine the

contents of multiple files (“catenate” means to join together). This command can be used to display contents of small files (that will fit on your terminal's display screen).

Example: cat hello.c (displays contents of c program

"hello.c")

more The more command displays a file, one

screenful at a time.

Example: more large_file

Movement keys (within more command): <spacebar> Move to next screen

b Move to previous screen<enter> Move to next line/car Search for pattern "car"q Exit to shell

less The less command is similar to more

command, but “less” command contains more movement and search commands than "more" command. “less” is available in bash, not ksh.

Example

less large_file

Note: You are not required to learn "less" command for this course, but if you are interested in using this command, you can refer to the online manual.

grep The grep command is used to search for

a pattern whether contained in files or from other forms of input (eg. keyboard).

Example: grep "frog" data (matches and displays lines in

file called "data" that contain pattern "frog")

Options: -c displays # of lines that contain a match -i ignores case sensitivity -v displays lines that do not match the pattern

head The head command displays the

beginning lines of a file. This command is useful to identify any heading information of a file.

example: head fname (displays the first 10 lines of

"fname")

Options: -n displays the first "n" number of lines

tail The tail command displays the ending

lines of a file. This command is useful for viewing files that continually add information to the bottom of a file such as log files (eg. Last person to logon, or last system message).

Example: tail fname (views the last 10 lines of "fname") Options: -n displays the last "n" number of lines +n displays all lines from line "n" to the end of the file

cp The cp command is used to copy one or

more files between directories, or to make backup copies of files within the same directory.

Example: cp /public/ipc144/hw.c /home/jsmith/

(copies file "hw.c" from “/public/ipc144" directory to jsmith’s home directory)

Options: -R subdirectories & contents are copied -i prompts user to overwrite existing file

mv The mv command is used to move or

rename files. Examples:

mv hw.c work(moves file "hw.c" from current directory to subdirectory called "work”, assuming directory “work” exists) mv hw.c hello.c(renames file "hw.c" in current directory to "hello.c”) Options:-i prompts user to overwrite existing file

ls The ls command is used to display

information regarding a file or directory.

Example: ls (Displays a compact listing (filenames only) contained in current directory, or in a specified directory) Options:

-a short display of all files (incl. hidden files)-l detailed display of files (excl. hidden files)-al detailed display of all files-F displays / after directory, * after executable file

sort The sort command is used to sort files. Very useful as a filter to sort output of

the previous command. Example: sort fname (alphabetically sorts (in ascending

order) the contents of "fname")

Options: -r sorts in reverse (descending order) -n sort numerically -kn Sorts by column number "n" -u sorts and only displays unique lines

diff The diff command displays the differences

between two files. If there are no differences in the files, there is no display. If there is a display the command provides instructions on how to make the first file identical to the second file.

Example:diff file1 file2

Getting Info About Users who finger

who Used to display names of users logged

into system.

Example: who

Options: -H displays headings above user information -i displays # of minutes user was idle

finger Used to display user names and

related information. Example: finger jsmith (Will provide information regarding user "jsmith")