Shells
A Command Interpreter processes these, when they are entered by users.
What are shell commands? What are commands?
What is /etc/profile?
What are the up and down arrow keys?
System-wide default environment variable settings are found in this file.
What is /etc/environment?
This command can break up a raw output line from another command into fields and filter the fields that it outputs.
What is cut?
Bash, Korn, and Fish are examples.
What is a shell?
Because we want PATH to be defined upon login, and we want it to be accessible to all subsequent non-login shells, we usually code our PATH overrides in this file.
What is .profile?
This environment variable controls the number of commands to be saved in the command history.
What is the HISTSIZE variable?
To get the value of a previously-set environment variable, precede the variable name with this character.
What is the dollar sign?
This command can filter the lines returned from another command by matching the content of each line with a regular expression.
What is grep?
When we want a subshell to have access to an environment variable we have set in our shell, we need to do this to the variable before starting the subshell.
What is export? What is exporting?
What are .bash_login and .profile?
To locate a previously-issued command in the command history and open it in a text editor, we use this command.
What is fc? What is fix command?
To set an environment variable to a value that contains embedded spaces, enclose the value in these.
What are quotes, quotation marks, or apostrophes?
This command can apply edits to each line of an input file and output the edited file.
What is sed?
What are external commands?
A subshell that does not process input from the user is called this.
What is a non-interactive shell?
The HISTCONTROL entry ignoreboth is shorthand for these two values.
What are ignorespaces and ignoredups?
The absolute path of the current user's home directory is stored in this environment variable, by convention.
What is HOME?
This command can string multiple files together end to end to form a single output file.
What is cat?
The process whereby the command interpreter matches a regular expression against filenames and passes the expanded filenames to the underlying command.
What is filename globbing? What is globbing?
Because this file is invoked for non-login interactive shells, people usually code settings that pertain to the display device here.
What is ~./bashrc?
To eliminate duplicate entries from the command history, we use this environment variable setting.
What is HISTCONTROL=erasedups
A reference to an environment variable prefixed with a dollar sign, when enclosed in quotation marks rather than apostrophes, will return this.
What is the variable's value?
This file can apply the output of diff to an original file, resulting in an output file with the differences resolved.
What is patch?