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layouts half of the linux fun ex

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## 12.9. practice: commands and arguments ## 12.9. practice: commands and arguments
1. How many arguments are in this line (not counting the command itself). touch '/etc/cron/cron.allow' 'file 42.txt' "file 33.txt" 1. How many arguments are in this line (not counting the command itself). `touch '/etc/cron/cron.allow' 'file 42.txt' "file 33.txt"`
2. Is tac a shell builtin command ? 2. Is `tac` a shell builtin command ?
3. Is there an existing alias for rm ? 3. Is there an existing alias for `rm`?
4. Read the man page of rm, make sure you understand the -i option of rm. Create and remove a file to test the -i option. 4. Read the man page of `rm`, make sure you understand the `-i` option of rm. Create and remove a file to test the -i option.
5. Execute: alias rm='rm -i' . Test your alias with a test file. Does this work as expected ? 5. Execute: `alias rm='rm -i'` . Test your alias with a test file. Does this work as expected?
6. List all current aliases. 6. List all current aliases.
7a. Create an alias called 'city' that echoes your hometown. 7a. Create an alias called `city` that echoes your hometown.
7b. Use your alias to test that it works. 7b. Use your alias to test that it works.
8. Execute set -x to display shell expansion for every command. 8. Execute `set -x` to display shell expansion for every command.
9. Test the functionality of set -x by executing your city and rm aliases. 9. Test the functionality of `set -x` by executing your city and rm aliases.
10 Execute set +x to stop displaying shell expansion. 10 Execute `set +x` to stop displaying shell expansion.
11. Remove your city alias. 11. Remove your city alias.
12. What is the location of the cat and the passwd commands ? 12. What is the location of the `cat` and the `passwd` commands?
13. Explain the difference between the following commands: 13. Explain the difference between the following commands:
* echo * `echo`
* /bin/echo * `/bin/echo `
14. Explain the difference between the following commands: echo Hello echo -n Hello 14. Explain the difference between the following commands:
* `echo Hello`
* `echo -n Hello `
15. Display A B C with two spaces between B and C. 15. Display A B C with two spaces between B and C.
(optional)16. Complete the following command (do not use spaces) to display exactly the following output: 16. (optional) Complete the following command (do not use spaces) to display exactly the following output:
```
4+4 =8 4+4 =8
10+14 =24 10+14 =24
17. Use echo to display the following exactly: ??\\ ```
17. Use `echo` to display the following exactly: `??\\`
## 13.9. practice: control operators ## 13.9. practice: control operators
0. Each question can be answered by one command line! 0. Each question can be answered by one command line!
1. When you type passwd, which file is executed ? 1. When you type `passwd`, which file is executed?
2. What kind of file is that? 2. What kind of file is that?
3. Execute the pwd command twice. (remember 0.) 3. Execute the `pwd` command twice. (remember 0.)
4. Execute ls after cd /etc, but only if cd /etc did not error. 4. Execute `ls` after `cd /etc`, but only if `cd /etc` did not error.
5. Execute cd /etc after cd etc, but only if cd etc fails. 5. Execute `cd /etc` after `cd etc,` but only if `cd etc` fails.
6. Echo it worked when touch test42 works, and echo it failed when the touch failed. All on one command line as a normal user (not root). Test this line in your home directory and in /bin/ . 6. Echo `it worked` when `touch test42` works, and echo `it failed` when the touch failed. All on one command line as a normal user (not root). Test this line in your home directory and in `/bin/`.
7. Execute sleep 6, what is this command doing ? 7. Execute `sleep 6`, what is this command doing ?
8. Execute sleep 200 in background (do not wait for it to finish). 8. Execute `sleep 200` in background (do not wait for it to finish).
9. Write a command line that executes rm file55. Your command line should print 'success' if file55 is removed, and print 'failed' if there was a problem. 9. Write a command line that executes `rm file55`. Your command line should print `success` if file55 is removed, and print `failed` if there was a problem.
(optional)10. Use echo to display "Hello World with strange' characters \ * [ } ~ \ \ ." (including all quotes) 10. (optional) Use echo to display `"Hello World with strange' characters \ * [ } ~ \ \ ."` (including all quotes)
## 14.13. practice: shell variables ## 14.13. practice: shell variables
1. Use echo to display Hello followed by your username. (use a bash variable!) 1. Use echo to display `Hello` followed by your `username`. (use a bash variable!)
2. Create a variable answer with a value of 42. 2. Create a variable `answer` with a value of 42.
3. Copy the value of $LANG to $MyLANG. 3. Copy the value of `$LANG` to `$MyLANG`.
4. List all current shell variables. 4. List all current shell variables.
5. List all exported shell variables. 5. List all exported shell variables.
6. Do the env and set commands display your variable ? 6. Do the `env` and `set` commands display your variable?
6. Destroy your answer variable. 6. Destroy your answer variable.
7. Create two variables, and export one of them. 7. Create two variables, and export one of them.
8. Display the exported variable in an interactive child shell. 8. Display the exported variable in an interactive child shell.
9. Create a variable, give it the value 'Dumb', create another variable with value 'do'. Use echo and the two variables to echo Dumbledore. 9. Create a variable, give it the value `Dumb`, create another variable with value `do`. Use `echo` and the two variables to `echo Dumbledore`.
10. Find the list of backslash escaped characters in the manual of bash. Add the time to your PS1 prompt. 10. Find the list of backslash escaped characters in the manual of bash. Add the time to your PS1 prompt.
## 15.3. practice: shell embedding ## 15.3. practice: shell embedding
1. Find the list of shell options in the man page of bash. What is the difference between set -u and set -o nounset? 1. Find the list of shell options in the man page of bash. What is the difference between `set -u` and `set -o nounset`?
2. Activate nounset in your shell. Test that it shows an error message when using non-existing variables. 2. Activate `nounset` in your shell. Test that it shows an error message when using non-existing variables.
3. Deactivate nounset. 3. Deactivate `nounset`.
4. Execute cd /var and ls in an embedded shell. The echo command is only needed to show the result of the ls command. Omitting will result in the shell trying to execute the first file as a command. 4. Execute `cd /var` and `ls` in an embedded shell. The echo command is only needed to show the result of the ls command. Omitting will result in the shell trying to execute the first file as a command.
5. Create the variable embvar in an embedded shell and echo it. Does the variable exist in your current shell now ? 5. Create the variable `embvar` in an embedded shell and echo it. Does the variable exist in your current shell now ?
6. Explain what "set -x" does. Can this be useful ? 6. Explain what `set -x` does. Can this be useful ?
(optional)7. Given the following screenshot, add exactly four characters to that command line so that the total output is FirstMiddleLast. 7. (optional) Given the following screenshot, add exactly four characters to that command line so that the total output is `FirstMiddleLast`. `[paul@RHEL4b ~]$ echo First; echo Middle; echo Last`
[paul@RHEL4b ~]$ echo First; echo Middle; echo Last 8. Display a long listing (`ls -l`) of the `passwd` command using the `which` command inside an embedded shell.
8. Display a long listing (ls -l) of the passwd command using the which command inside an embedded shell.
## 16.12. practice: shell history ## 16.12. practice: shell history
1. Issue the command echo The answer to the meaning of life, the universe and everything is 42. 1. Issue the command `echo The answer to the meaning of life, the universe and everything is 42.`.
2. Repeat the previous command using only two characters (there are two solutions!) 2. Repeat the previous command using only two characters (there are two solutions!)
3. Display the last 5 commands you typed. 3. Display the last 5 commands you typed.
4. Issue the long echo from question 1 again, using the line numbers you received from the command in question 3. 4. Issue the long echo from question 1 again, using the line numbers you received from the command in question 3.
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1. Create a test directory and enter it. 1. Create a test directory and enter it.
2. Create the following files : (the last one has 6 characters including a space) 2. Create the following files : (the last one has 6 characters including a space)
* file1 * `file1`
* file10 * `file10`
* file11 * `file11`
* file2 * `file2`
* File2 * `File2`
* File3 * `File3`
* file33 * `file33`
* fileAB * `fileAB`
* filea * `filea`
* fileA * `fileA`
* fileAAA * `fileAAA`
* file( * `file(`
* file 2 * `file 2`
3. List (with ls) all files starting with file 3. List (with ls) all files starting with file
4. List (with ls) all files starting with File 4. List (with ls) all files starting with File
5. List (with ls) all files starting with file and ending in a number. 5. List (with ls) all files starting with file and ending in a number.
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11. List (with ls) all files that start with f or F and end with 3 or A. 11. List (with ls) all files that start with f or F and end with 3 or A.
12. List (with ls) all files that start with f have i or R as second character and end in a number. 12. List (with ls) all files that start with f have i or R as second character and end in a number.
13. List all files that do not start with the letter F. 13. List all files that do not start with the letter F.
14. Copy the value of $LANG to $MyLANG. 14. Copy the value of `$LANG` to `$MyLANG`.
15. Show the influence of $LANG in listing A-Z or a-z ranges. 15. Show the influence of `$LANG` in listing A-Z or a-z ranges.
16. You receive information that one of your servers was cracked, the cracker probably replaced the ls command. You know that the echo command is safe to use. Can echo replace ls ? How can you list the files in the current directory with echo ? 16. You receive information that one of your servers was cracked, the cracker probably replaced the `ls` command. You know that the `echo` command is safe to use. Can echo replace ls ? How can you list the files in the current directory with echo?
17. Is there another command besides cd to change directories ? 17. Is there another command besides `cd` to change directories?
## 18.9. practice: input/output redirection ## 18.9. practice: input/output redirection
1. Activate the noclobber shell option. 1. Activate the `noclobber` shell option.
2. Verify that noclobber is active by repeating an ls on /etc/ with redirected output to a file. 2. Verify that `noclobber` is active by repeating an `ls` on `/etc/` with redirected output to a file.
3. When listing all shell options, which character represents the noclobber option ? 3. When listing all shell options, which character represents the `noclobber` option ?
4. Deactivate the noclobber option. 4. Deactivate the `noclobber` option.
5. Make sure you have two shells open on the same computer. Create an empty tailing.txt file. Then type tail -f tailing.txt. Use the second shell to append a line of text to that file. Verify that the first shell displays this line. 5. Make sure you have two shells open on the same computer. Create an empty tailing.txt file. Then type `tail -f tailing.txt`. Use the second shell to append a line of text to that file. Verify that the first shell displays this line.
6. Create a file that contains the names of five people. Use cat and output redirection to create the file and use a here document to end the input. 6. Create a file that contains the names of five people. Use `cat` and output redirection to create the file and use a here document to end the input.
## 19.13. practice: filters ## 19.13. practice: filters
1. Put a sorted list of all bash users in bashusers.txt. 1. Put a sorted list of all bash users in `bashusers.txt`.
2. Put a sorted list of all logged on users in onlineusers.txt. 2. Put a sorted list of all logged on users in `onlineusers.txt`.
3. Make a list of all filenames in /etc that contain the string conf in their filename. 3. Make a list of all filenames in `/etc` that contain the string `conf` in their filename.
4. Make a sorted list of all files in /etc that contain the case insensitive string conf in their filename. 4. Make a sorted list of all files in `/etc` that contain the case insensitive string `conf` in their filename.
5. Look at the output of /sbin/ifconfig. Write a line that displays only ip address and the subnet mask. 5. Look at the output of `/sbin/ifconfig`. Write a line that displays only ip address and the subnet mask.
6. Write a line that removes all non-letters from a stream. 6. Write a line that removes all non-letters from a stream.
7. Write a line that receives a text file, and outputs all words on a separate line. 7. Write a line that receives a text file, and outputs all words on a separate line.
8. Write a spell checker on the command line. (There may be a dictionary in /usr/share/dict/ .) 8. Write a spell checker on the command line. (There may be a dictionary in `/usr/share/dict/`.)
## 20.11. practice: basic Unix tools ## 20.11. practice: basic Unix tools
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6. Here are two commands that do the same thing: copy `*.odf` files to /backup/ . What would be a reason to replace the first command with the second ? Again, this is an important question. 6. Here are two commands that do the same thing: copy `*.odf` files to /backup/ . What would be a reason to replace the first command with the second ? Again, this is an important question.
* `cp -r /data/*.odf /backup/` * `cp -r /data/*.odf /backup/`
* `find /data -name "*.odf" -exec cp {} /backup/ \;` * `find /data -name "*.odf" -exec cp {} /backup/ \;`
7. Create a file called loctest.txt. Can you find this file with locate ? Why not ? How do you make locate find this file ? 7. Create a file called `loctest.txt`. Can you find this file with `locate`? Why not? How do you make locate find this file ?
8. Use find and -exec to rename all .htm files to .html. 8. Use `find` and `-exec` to rename all .htm files to .html.
9. Issue the date command. Now display the date in YYYY/MM/DD format. 9. Issue the `date` command. Now display the date in YYYY/MM/DD format.
10. Issue the cal command. Display a calendar of 1582 and 1752. Notice anything special ? 10. Issue the `cal` command. Display a calendar of 1582 and 1752. Notice anything special ?
## 22.19. practice: vi(m) ## 22.19. practice: vi(m)
1. Start the vimtutor and do some or all of the exercises. You might need to run aptitude install vim on xubuntu. 1. Start the `vimtutor` and do some or all of the exercises. You might need to run `aptitude install vim` on xubuntu.
2. What 3 key sequence in command mode will duplicate the current line. 2. What 3 key sequence in command mode will duplicate the current line.
3. What 3 key sequence in command mode will switch two lines' place (line five becomes line six and line six becomes line five). 3. What 3 key sequence in command mode will switch two lines' place (line five becomes line six and line six becomes line five).
4. What 2 key sequence in command mode will switch a character's place with the next one. 4. What 2 key sequence in command mode will switch a character's place with the next one.
5. vi can understand macro's. A macro can be recorded with q followed by the name of the macro. So qa will record the macro named a. Pressing q again will end the recording. You can recall the macro with @ followed by the name of the macro. Try this example: i 1 'Escape Key' qa yyp 'Ctrl a' q 5@a (Ctrl a will increase the number with one). 5. vi can understand macro's. A macro can be recorded with q followed by the name of the macro. So qa will record the macro named a. Pressing q again will end the recording. You can recall the macro with @ followed by the name of the macro. Try this example: i 1 'Escape Key' qa yyp 'Ctrl a' q 5@a (Ctrl a will increase the number with one).
6. Copy /etc/passwd to your ~/passwd. Open the last one in vi and press Ctrl v. Use the arrow keys to select a Visual Block, you can copy this with y or delete it with d. Try pasting it. 6. Copy `/etc/passwd` to your `~/passwd`. Open the last one in vi and press Ctrl v. Use the arrow keys to select a Visual Block, you can copy this with y or delete it with d. Try pasting it.
7. What does dwwP do when you are at the beginning of a word in a sentence ? 7. What does dwwP do when you are at the beginning of a word in a sentence ?
## 23.9. practice: introduction to scripting ## 23.9. practice: introduction to scripting