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28 Cards in this Set
- Front
- Back
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How to I permanently delete a variable from my system for all users? |
NOTE If you want a variable assignment to be removed permanently, you must remove the assignment from the configuration file and from memory. You would issue the command unset <variable_name> and then delete the statement that creates the variable in the configuration file (/etc/profile or ~/.bash_profile). |
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When you execute a command, be sure to test the results. For example, if you are asked to open a child shell, you should follow this procedure: |
1. Verify the process ID (PID) of the current shell using the ps or ps -f command. 2. Create the child process (bash). 3. Verify you are in a child shell by executing the ps -f command and then look for a PID whose parent process (PPID) is the same as you verified in step 1. |
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Can you name the five bash configuration files? |
/etc/profile /etc/bashrc ~/.bash_profile ~/.bashrc ~/.bash.logout |
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What are four important variables found in /etc/profile? |
HOSTNAME HISTCONTROL HISTSIZE umask |
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What directory contains application files for operation? What are two examples of application files? |
/etc/bashrc ~/.toprc configures how top command operates ~/.exrc. Configures how vi operates |
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What are the four configuration elements found in /etc/bashrc? |
Aliases Functions Shell configuration options PS1 prompt configuration |
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What does the ~/.bash_profile contain and when is it read? |
It contains user specific customizations to the bash environment, such as time zone, locale, and editor).
It is only read if the user logs onto the system and his default shell is bash. This, changes will not be read until the users next logon OR the command source~/.bash_profile is run. |
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What is /etc/profile.d What does it contain? When is it read? What suffix of files does it read? |
It contains configuration information for certain programs They are read during the login process etc/profile contains a statement to read files with the suffix .sh for bash/bourne,/Korn users. For C shell users, csh.login contains a statement to read files with the suffix .csh |
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Configuration files are not active until... How is this done? |
They are stored in memory. source<filename> or .<filename> |
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What is the default standard input device? What is the default standard output device? What is the default standard error device? |
The keyboard The monitor The monitor |
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What is redirection in relation to default devices? |
It allows the user to alter the stdin, stdout, or stderr device or file. |
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A file descriptor is... And what are the file descriptor numbers? |
A reference, also known as a handle, used by the kernel to access a file. fd0 for stdin fd1 for stdout fd2 for stderr fd255 this file descriptor keeps track of controlling terminal information |
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How can I see the terminal devices? (There are two ways)
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in the filling directories:/dev/pts /#/dev/tty /dev/console /dev/ttyS Or command: tty |
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What is the /dev directory used for? Why is this significant for the test? |
It provides a path to a device. The test uses the dircoties as the terminal device name /dev/tty0 and /dev/tty1 More accurate names for the devices would be tty0 and tty1 |
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How many virtual text terminals does Linux provide? How are they named? |
62 Either /dev/tty# or /dev/vc/# |
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What file names are attached to the current process? |
/dev/tty and /dev/tty0 |
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What does /dev/ttyS refer to? |
The systems serial ports |
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How can I change, or specify, or add multiple console devices? |
console=<device>, <deviceoptions> |
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How can I have message printed on tty1 and and the current terminal device (tty0)? |
Add console=/dev/tty1 console=/dev/tty0 to the kernel command line |
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What is the purpose of /dev/null? |
To prevent stdout and stderr message from being written to tty0. |
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What is the keyboards file descriptor number? Device name? |
0 fd0 |
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How can I choose an alternate standard input device for a particular command? |
< << For example cat < /etc/hosts makes cat recieve input from the /etc/hosts rather than the keyboard. |
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What parameter can I set to avoid accidently overwriting a file? Hwo can I check if this parameter is set? How can I turn the parameter off? |
command: noclobber Set -o | grep noclobber set +o noclobber |
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What is the default standard error device?
Whats the name of the device, in the context of stderr? |
The monitor
fd2 |
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What are the names for The stdin The stdout The stderr |
fd0 fd1 fd2 |
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What is the difference between the output file and the standard device for stdin, stdout, and stderr? |
None. If > or >> for stdout and 2> and 2>> are used to redirect the output to another "device" that is the same as choosing another file. Thus, the default device is no longer the monitor, bit is the file or new device, whatever you want to call it. Everything is a file. |
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What is the functional name of > 2> 2>&1 |
Control operators |
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How do I write the standard output and the standard error to the same file? How do I redirect them? (So that I don't overwrite the new device) |
2>&1
For example ls -ld /etc /roses 2>&1 errorfile (Roses doesn't exist in the above example so it will have an error message) The same command as above but replace 2>&1 with >& |
