Hello, JakobYour operating system likely provides a convenient, mouse-based and graphical means to interact with your file system.
I was so blinded by the first thing they showed me, which was the graphical user interface. I thought it was the best thing I’d ever seen in my life. – Steve Jobs on one of the early GUI systems
Today, we’ll introduce how to do the same operations and more via the terminal.
For now, think of the terminal simply as a text-based way for you to invoke programs. These programs each,
cd),== CommandsOne note on terminology:
The programs we’ll be using are often referred to as commands.1
Here we invoke a program, cp, which copies note.txt into the directory notes/, but doesn’t override the file if it already exists there.
At a high level, we invoke a program (issue a command) with,
Programs are unlike functions in R. They do not receive typed objects as arguments, but merely a list of strings. Here’s an example.
// hello.cpp
#include <iostream>
auto main(int argc, char** argv) -> int {
if (argc == 2) {
std::cout << "Hello, " << argv[1] << '\n';
}
}Compiling the program:
Running it with the argument, Jakob.
Hello, JakobTo better demonstrate, here’s a program that simply prints all its arguments.
// print_all.cpp
#include <iostream>
auto main(int argc, char** argv) -> int {
for (int i = 0; i < argc; ++i) {
std::cout << "Argument #" << i << ": " << argv[i] << '\n';
}
}As you can see, the program has free rein to do whatever it likes with the strings (arguments) you pass.
Thankfully there are a set of conventions.
Program options are often akin to named arguments in R. That is, they are key-value pairs.
Or sometimes you will need to set it with an = right after the key name, i.e.,
Some options are not key-value pairs. Instead, their presence alone informs the program to do something. These are called flags.
Notice that we called the previous arguments options. They are called as such as they are optional.
Some arguments are required. These are typically provided based on position.
Enter man <program> to pull up the manual for a particular command.
Here’s an example from the command ls:
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
--author
with -l, print the author of each file
-b, --escape
print C-style escapes for nongraphic characters
--block-size=SIZE
with -l, scale sizes by SIZE when printing them; e.g.,
'--block-size=M'; see SIZE format belowNotice that many arguments have both verbose and shorthand versions (e.g., -A vs. --almost-all).
Many programs also have a --help option to output a usage guide instead of running the program as usual.
Remember, these are just conventions, not rules.
Always check the documentation.
Think of your terminal as existing inside a directory (folder). All commands issued will be relative to this position.
We call this the,
current working directory.
Use the command pwd to print the current working directory.
Importantly, we use,
. (one period) to refer to the current working directory (often implicit)... (two periods) to refer to the parent directory.Consider the following directory structure:
Consider the following directory structure:
- stuff
todo.txt
- books <- suppose this is the current working directory
- moby_dick.pdf
- obedience_to_authority.pdf
- little_women.pdf
- school
- stat133.pdf
- code
- hack_nsa.cpp
- ai_friend.pyWhich path should I provide to refer to hack_nsa.cpp?
../code/hack_nsa.cpp
Consider the following directory structure:
- stuff
todo.txt
- books
- moby_dick.pdf
- obedience_to_authority.pdf
- little_women.pdf
- school <- suppose this is the current working directory
- stat133.pdf
- code
- hack_nsa.cpp
- ai_friend.pyWhich path should I provide to refer to todo.txt?
../../todo.txt
Is ../../../stuff/code/../todo.txt equivalent?
Consider the following directory structure:
- stuff <- suppose this is the current working directory
todo.txt
- books
- moby_dick.pdf
- obedience_to_authority.pdf
- little_women.pdf
- school
- stat133.pdf
- code
- hack_nsa.cpp
- ai_friend.pyWhich path should I provide to refer to stat133.pdf?
./books/school/stat133.pdf
Is books/school/stat133.pdf equivalent?
It would be inconvenient if we were stuck in one directory. We can change our current working directory with the commmand cd.
- stuff <- suppose this is the current working directory
todo.txt
- books
- moby_dick.pdf
- obedience_to_authority.pdf
- little_women.pdf
- school
- stat133.pdf
- code
- hack_nsa.cpp
- ai_friend.pyWhat’s our working directory after running the following line?
cd ../stuff/./code/../books/school/../../.,
stuff
Below you’ll find a list of helpful commands you should be aware of (you can scroll).
mkdir <options> <directory>: Make a directory <directory>.rm <options> <file or directory>: Remove files or directories. Use the flag -r (recursive) to remove directories – be careful!ls <options> <file or directory>: List information about files or directories. If not specified, the current directory is used.cp <options> <source> <destination>: Copy file(s) <source> to <destination>. Destination can be a file name or directory.mv <options> <source> <destination>: Move file(s) <source> to <destination> (or equivalently, rename the file from <source>touch <file>: Create an empty file named <file>.cat <file>: Print the contents of <file> to the terminal.head <file>: Print the first part of <file> to the terminal.tail <file>: Print the last part of <file> to the terminal.cd <directory>: Change the current working directory to <directory>.pwd: Print the current working directory to the terminal. to <destination>.My primary tip is this: don’t add spaces to file or directory names!
If you do this, you will be required to add quotes to refer to the name. Compare:
I also prefer prepending 0s to ordered names to ensure they are ordered when listed.