This is Lab Worksheet 5 - not an Assignment

This Lab Worksheet contains some practical examples that will prepare you to complete your Assignments.
You do not have to hand in this Lab Worksheet. Make sure you complete the separate Assignments on time. Quizzes and tests may refer to work done in this Lab Worksheet; save your answers.

Before you get started - REMEMBER TO READ ALL THE WORDS

You must have an account on the Course Linux Server to do this lab. Log in to the server and use the shell. Review the Class Notes related to this worksheet as you work through it. Leave your work on the Linux server. Do not delete any work from the Linux server until the term is over and your marks are complete!

Commands introduced and used in this Lab

• alias – (man bash) built-in bash command to create synonyms for command names.

• bash – Linux full-featured Bourne-Again SHell for interactive use

• bash – Shell aliases

• bash – Shell command history !! !120

• bash – Shell command pipelining: |

• bash – Shell curly brace expansion: {...,...}

• bash – Shell I/O redirection: > < >>

• bash – Shell wildcard (GLOB char) patterns: * ? [...] [!...]

• dash – smaller Bourne-like shell for use in scripts (may be linked to from /bin/sh).

• date – show the current time and date

• head – select lines at the start (head) of the input (default is to select first 10 lines)

• nl – read lines and prefix them with line numbers (see also: cat -n )

• sum – generate a checksum

• tail – select lines at the end (tail) of the input (default is to select last 10 lines)

• wc – count lines, words, and characters

Log in to the Course Linux Server to do all commands in this lab. Set your bash PS1 shell prompt to show your login name, computer name, and the basename of your current directory, just as you did in the previous Lab. Leave your finished work on the server; do not delete it when you are finished the worksheet.

Using Wildcards (GLOB chars) in Pathname Specifications

Use the echo command to see how patterns expand first, before you use them in a real command line, e.g.

• echo /etc/pas* ; echo /dev/sd* ; echo /bin/*sh

Do not use character ranges, especially alphabetic ranges, without first understanding your system LOCALE setting. The range [a-z] often includes the upper-case letters from B through Z and may not include A.

Use the echo command to see how patterns expand first, before you use them in a real command line.

Lab5.1: Using ? to match any single character

As we do with most sections of each lab, we recursively remove and recreate a directory in which to do this section. This lets you return to this place and redo a section without having files left over from previous work.

[user@localhost ]$ cd ; rm -rf lab5.1 ; mkdir lab5.1 ; cd lab5.1

[user@localhost lab5.1]$ touch f1 f2 f3

[user@localhost lab5.1]$ touch f10 f20 f30

[user@localhost lab5.1]$ touch f11 f12 f13

[user@localhost lab5.1]$ touch f33 fffff

[user@localhost lab5.1]$ mkdir dir1 dir2 dir3

[user@localhost lab5.1]$ ls

dir1 dir2 dir3 f1 f10 f11 f12 f13 f2 f20 f3 f30 f33 fffff

[user@localhost lab5.1]$ ls | sum

33442 1 ( make sure you get this number, otherwise start over at the beginning)

Use the echo command to see how patterns expand first, before you use them in a real command line.

[user@localhost lab5.1]$ cp f? dir1

1. Which files have been copied to the directory dir1? (First try to answer without typing the command.)

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[user@localhost lab5.1]$ cp f?0 dir2

2. Which files have been copied to the directory dir2? (First try to answer without typing the command.)

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[user@localhost lab5.1]$ cp f?3 dir3

3. Which files have been copied to the directory dir3? (First try to answer without typing the command.)

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[user@localhost lab5.1]$ echo ? ?? ?????

4. One of the above three patterns fails to expand to any pathname. Which pattern, and why?

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[user@localhost lab5.1]$ cp ? ?? ????? dir3

5. Why does the above command line give an error message from the copy command?

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[user@localhost lab5.1]$ ls /dev/tty*

6. The above command shows all terminal devices configured in your Linux system. Try it.
   What command line, similar to the above, shows only the five-character terminal device names,
   i.e. shows tty10 and tty63 and ttyS0, etc. but does not show tty or tty1 or tty9 etc.?

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Lab5.2: Using * to match zero or more characters

This section depends on the files created at the start of section 1.1. Create those files first.

[user@localhost lab5.1]$ cd ; rm -rf lab5.2 ; mkdir lab5.2 ; cd lab5.2

[user@localhost lab5.2]$ cp -a ../lab5.1/. . (note the single dot destination directory)

[user@localhost lab5.2]$ ls

dir1 dir2 dir3 f1 f10 f11 f12 f13 f2 f20 f3 f30 f33 fffff

[user@localhost lab5.2]$ ls | sum

33442 1 ( make sure you get this number, otherwise start over at the beginning of 1.1)

Use the echo command to see how patterns expand first, before you use them in a real command line.

[user@localhost lab5.2]$ rm dir?/* (clean out all files in these directories)

[user@localhost lab5.2]$ ls f*

1. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.2]$ ls -d d*

2. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.2]$ ls f*1 (that pattern contains a digit, not a letter)

3. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.2]$ ls -d *1 (that pattern contains a digit, not a letter)

4. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.2]$ ls -d *1* (that pattern contains a digit, not a letter)

5. What is the output of the last command, above? (First try to answer without typing the command.)

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Lab5.3: Using [ ] to match a single character from a list of characters

[user@localhost ]$ cd ; rm -rf lab5.3 ; mkdir lab5.3 ; cd lab5.3

[user@localhost lab5.3]$ touch hat help hit hot hut

[user@localhost lab5.3]$ ls | sum

07916 1 ( make sure you get this number, otherwise start over at the beginning of 1.3)

Use the echo command to see how patterns expand first, before you use them in a real command line.

[user@localhost lab5.3]$ ls h[ao]t

6. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.3]$ ls h[aeiou]t

7. What is the output of the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.3]$ ls h[aeiou]*

8. Comparing with the previous output, which additional file is displayed? ___________________

9. Why? ______________________________________________________________________________

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[user@localhost lab5.3]$ cd ; rm -rf lab5.3b ; mkdir lab5.3b ; cd lab5.3b

[user@localhost lab5.3b]$ touch sda sdb sdc sdd

[user@localhost lab5.3b]$ touch sda1 sdb2 sdc3 sdd4

[user@localhost lab5.3b]$ ls | sum

61395 1 ( make sure you get this number, otherwise start over at the beginning of 1.3)

[user@localhost lab5.3b]$ ls sd[abc]

10. Which names are output by the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.3b]$ ls sda[1-4]

11. Which names are output by the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.3b]$ ls sd[bc][1-3]

12. Which names are output by the last command, above? (First try to answer without typing the command.)

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[user@localhost lab5.3b]$ echo sd[^ab][^12]

13. Which names are output by the last command, above? (First try to answer without typing the command.)

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Character ranges [a-z] are dangerous! Always test them first!

Do not use character ranges, especially alphabetic ranges, without first understanding your system LOCALE setting. The range [a-z] often includes the upper-case letters from B through Z and may not include A. Try the following test on your Fedora 12 system and also on the Course Linux Server and note the differences:

1. $ touch a A b B y Y z Z

2. fedora$ echo [a-z] # Fedora gives: a b y z

3. fedora$ echo [A-Z] # Fedora gives: A B Y Z

4. ubuntu$ echo [a-z] # Ubuntu gives: a B b Y y Z z

5. ubuntu$ echo [A-Z] # Ubuntu gives: A a B b Y y Z

Fedora uses an old English-only LOCALE that expects ASCII characters where Ubuntu uses a modern International LOCALE that also includes Unicode characters. Do not use character ranges, especially alphabetic ranges, without first understanding your system LOCALE setting.

Using Shell I/O Redirection

• Shell I/O redirection can appear anywhere in the command line, even at the very beginning.

• The redirection syntax is removed from the command line before calling the command to run, so it is not counted as an argument on the command line. The command knows nothing about it.

• Redirection happens first, before the command runs. Redirection files are erased to empty even if the command is not found or has no output. This truncation happens before the command runs.

Lab5.4: Redirection happens first, before the command runs

[user@localhost ]$ cd ; rm -rf lab5.4 ; mkdir lab5.4 ; cd lab5.4

[user@localhost lab5.4]$ date > foo (erase foo and then put the date in it)

[user@localhost lab5.4]$ cat foo foo foo (show the file contents three times)

[user@localhost lab5.4]$ cat foo foo foo >foo (send foo into foo three times)

[user@localhost lab5.4]$ cat foo (what is in foo now?)

1. Explain in detail what you see inside the file foo now and exactly how the contents got that way:

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Creating a text file from keyboard input using keyboard EOF ^D

• Most Unix/Linux commands that read data from file names as arguments will read your keyboard (“standard input”) if you don't supply any file names to read. Examples: cat, wc, sum, sort, grep
  
  

[user@localhost lab5.4]$ cat > myfile (no file names are given to the cat command)

The cursor waits at the beginning of the next line for input from the keyboard. No prompt appears!

Type: Hello world!

Press [Enter]

Press [Ctrl]+d (hold Ctrl down and then press the d key to close the keyboard and send EOF)

[user@localhost lab5.4]$ cat myfile (This is Output One.)

Note the output of the above command. This is Output One.

[user@localhost lab5.4]$ cat > myfile (no file names are given to the cat command)

Type your name. (No prompt appears! You are typing directly into the cat program.)

Press [Enter]

Press [Ctrl]+d (hold Ctrl down and then press the d key to close the keyboard and send EOF)

[user@localhost lab5.4]$ cat myfile (This is Output Two.)

1. Explain exactly why does Output Two show none of the text from Output One?

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Appending to or Overwriting an existing file using > and >>

[user@localhost lab5.4]$ date > bar (note only one > on this line!)

[user@localhost lab5.4]$ date >> bar

[user@localhost lab5.4]$ date > bar (note only one > on this line!)

[user@localhost lab5.4]$ date >> bar

[user@localhost lab5.4]$ date >> bar

1. How many lines are in output file bar now (guess without executing commands first)? ____________

Concatenating multiple files using cat

[user@localhost lab5.4]$ cat > f1

Enter the following keyboard text (and close the file as before using EOF): Hello everybody

[user@localhost lab5.4]$ cat > f2

Enter the following keyboard text (and close the file as before using EOF): My name is My Name

[user@localhost lab5.4]$ cat > f3

Enter the following keyboard text (and close the file as before using EOF): Good-bye

[user@localhost lab5.4]$ cat f1 f2 f3 > f4

1. Describe the contents of file f4 after the last command, above. What happened?

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Lab5.5: Using shell pipelines | to connect commands

[user@localhost ]$ cd ; rm -rf lab5.5 ; mkdir lab5.5 ; cd lab5.5

[user@localhost lab5.5]$ ls -l /bin (too much output to see on one screen)

[user@localhost lab5.5]$ ls -l /bin | less

Use the [spacebar] to jump to the next screen of information in less. You can use q to exit the command.

[user @localhost lab5.5]$ grep 'the' /etc/fstab

[user @localhost lab5.5]$ grep 'none' /etc/fstab

[user @localhost lab5.5]$ grep 'the' /etc/fstab | grep 'none'

1. The first two commands show output, so why is there no output from the last command pipeline, above?

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[user@localhost lab5.5]$ nl /etc/passwd

[user@localhost lab5.5]$ nl /etc/passwd | head -n 5

[user@localhost lab5.5]$ nl /etc/passwd | head -n 5 | tail -n 1

2. Describe concisely what the last pipeline above selects from any input file (read some man pages first):

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Using shell aliases

Aliases let you define your own command names. You can also redefine existing command names and/or add your favourite options. Many Linux systems come with some aliases defined already. These predefined aliases may be set in system RC files (under /etc) or in a .bashrc file placed into your account HOME directory.

Listing all current shell aliases

[user@localhost lab5.5]$ alias (list all current aliases - may be none)

[user@localhost lab5.5]$ grep -w 'alias' /etc/skel/.bashrc

[user@localhost lab5.5]$ grep -w 'alias ls=' /etc/skel/.bashrc

1. Record the output of the last command, above: _______________________________

2. Give a two-command shell pipeline that would count the number of aliases in /etc/skel/.bashrc

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Creating a shell alias (for this shell only)

[user@localhost lab5.5]$ alias myls='ls -alF --color=auto'

[user@localhost lab5.5]$ alias | grep 'myls'
[user@localhost lab5.5]$ ls .. (two dots - parent directory)

[user@localhost lab5.5]$ myls .. (two dots - parent directory)

1. Describe how typing myls gives different output compared to typing ls:

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Removing a single shell alias (for this shell only)

[user@localhost lab5.5]$ alias myls='ls -alF --color=auto'

[user@localhost lab5.5]$ myls

[user@localhost lab5.5]$ unalias myls

[user@localhost lab5.5]$ alias | grep 'myls'

[user@localhost lab5.5]$ myls

1. Record exactly the error message from using the undefined alias (undefined command name):

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Temporarily bypassing a current alias using backslash

Putting a backslash in front of a command name causes the shell to ignore any alias for that command.

[user@localhost lab5.5]$ alias ls='ls -alF --color=auto'

[user@localhost lab5.5]$ ls .. (two dots - parent directory)

[user@localhost lab5.5]$ \ls .. (two dots - parent directory)

1. Describe how typing \ls gives different output compared to typing the aliased version of ls:

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2. Given what you see above, what is the function of the backslash character \ in front of an alias?

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3. Give a command to remove the ls alias: ________________________________________

4. What command will remove all current aliases (RTFM): _____________________________

Lab5.6: Curly Brace Expansion - {...,...}

Curly braces surround comma-delimited text that you want the shell to repeat. The pattern foo{1,2,3} is expanded to be three arguments foo1 foo2 foo3 by the shell. Blanks inside the braces need to be quoted to hide them from the shell. You can nest braces: foo{bar{1,2,3},more{a,b},end}

Use the echo command to see how patterns expand first, before you use them in a real command line.

[user@localhost ]$ cd ; rm -rf lab5.6 ; mkdir lab5.6 ; cd lab5.6

[user@localhost lab5.6]$ echo foo{1,2,3} bar{fly,maid,tender,stool}

[user@localhost lab5.6]$ echo foo{bar{1,2,3},more{a,b},end}

[user@localhost lab5.6]$ touch file{a,b,c} in{1,2,3}days

1. Record the six files that were created by the above command (guess without executing commands first):

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[user@localhost lab5.6]$ rm fil{ea,eb} i{n1,n2}days

2. Which files were removed by the above command? (First try to answer without typing the command.)

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IMPORTANT: Make sure all the braces match and that there are NO BLANKS inside the following pattern:

[user@localhost]$ mkdir -p lab5/{old,new}/{lab{1,2},theory{1,2},test{1,2}}

3. How many directories and sub-directories in total have been created by the above command? _______

4. What two-command pipeline could be used to find all the pathnames in the lab5 directory and then count them, outputting just a single number for the count of pathnames (same answer as previous question)?
   (Hint: What command finds pathnames? What command counts lines? See your previous labs!)

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Review: Basic Commands

5. How do mv and cp differ?

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6. Describe the purpose of the whoami command (read the man page):

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7. Describe the purpose of the command: head

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8. What is the purpose of the -i switch (option) to the ls command?

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9. What is the purpose of the -d switch (option) to the ls command?

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10. Describe the purpose of the command: grep

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11. Describe the purpose of the wc command:

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12. What command name and options copy an entire directory, including all the other files and sub-directories stored under it?

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13. What command name do you use to delete/remove an empty directory?

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14. What command name and options do you use to delete/remove a complete directory structure including all the other files and sub-directories stored under it?

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15. What command name and options would find any pathname ending in the basename of passwd, found in any directory, starting from the ROOT directory?

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16. What command name and options would find and print all the pathnames under the directory /etc?

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17. What command would find and print all the pathnames owned by the root user under /var/spool:

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18. How do you create a directory a/b/c/d/e including all the parent directories, in one command line?

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19. Use a head and tail pipeline to show only lines 10-20 from the file /etc/passwd:

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20. Use a head and tail and sort pipeline to show only lines 10-20 from the file /etc/passwd, sorted in descending (not ascending) order (read the sort man page):

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21. Rewrite the pathname /usr/./bin/../local/./bin/../sbin as a simple absolute pathname, without using any “.” or “..”:

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