--- /dev/null
+# Basic Shell Commands
+***
+
+## 1. Shell Basics:
+
+| Command | Definition |
+|----------------|----------------------------------------------------------------------------------------------------------------|
+| `.` | a single period refers to the current directory |
+| `..` | a double period refers to the directory immediately above the current directory |
+| `~` | refers to your home directory. _Note:_ this command does NOT work on Windows machines (Mac and Linux are okay) |
+| `cd ./dirname` | changes the current directory to the directory `dirname` |
+| `ls -F` | tells you what files and directories are in the current directory |
+| `pwd` | tells you what directory you are in (`pwd` stands for *p*rint *w*orking *d*irectory) |
+| `history` | lists previous commands you have entered. `history | less` lets you page through the list. |
+| `man` *cmd* | displays the *man*ual page for a command. |
+
+
+
+## 2. Creating Things:
+### a) How to create new files and directories..
+
+| Command | Definition |
+|-------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `mkdir ./dirname` | makes a new directory called dirname below the current directory. _Note:_ Windows users will need to use `\` instead of `/` for the path separator |
+| `nano filename` | if `filename` does not exist, `nano` creates it and opens the `nano` text editor. If the file exists, `nano` opens it. _Note:_ _(i)_ You can use a different text editor if you like. In gnome Linux, `gedit` works really well too. _(ii)_ `nano` (or `gedit`) create text files. It doesn't matter what the file extension is (or if there is one) |
+
+### b) How to delete files and directories...
+#### _Remember that deleting is forever. There is NO going back_
+
+| Command | Definition |
+|-------------------|------------------------------------------------------------------------------------------------------------------|
+| `rm ./filename` | deletes a file called `filename` from the current directory |
+| `rmdir ./dirname` | deletes the directory `dirname` from the current directory. _Note:_ `dirname` must be empty for `rmdir` to run. |
+
+### c) How to copy and rename files and directories...
+
+| Command | Definition |
+|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `mv tmp/filename .` | moves the file `filename` from the directory `tmp` to the current directory. _Note:_ _(i)_ the original `filename` in `tmp` is deleted. _(ii)_ `mv` can also be used to rename files (e.g., `mv filename newname` |
+| `cp tmp/filename .` | copies the file `filename` from the directory `tmp` to the current directory. _Note:_ _(i)_ the original file is still there |
+
+
+
+## 3. Pipes and Filters
+### a) How to use wildcards to match filenames...
+Wildcards are a shell feature that makes the command line much more powerful than any GUI file managers.
+Wildcards are particularly useful when you are looking for directories, files, or file content that can
+vary along a given dimension. These wildcards can be used with any command that accepts file names or
+text strings as arguments.
+
+#### Table of commonly used wildcards
+
+| Wildcard | Matches |
+|------------------------|------------------------------------------------|
+| `*` | zero or more characters |
+| `?` | exactly one character |
+| `[abcde]` | exactly one of the characters listed |
+| `[a-e]` | exactly one character in the given range |
+| `[!abcde]` | any character not listed |
+| `[!a-e]` | any character that is not in the given range |
+| `{software,carpentry}` | exactly one entire word from the options given |
+
+See the cheatsheet on regular expressions for more "wildcard" shortcuts.
+
+### b) How to redirect to a file and get input from a file ...
+Redirection operators can be used to redirect the ouput from a program from the display screen to a file where it is saved (or many other places too, like your printer or to another program where it can be used as input).
+
+
+| Command | Description |
+|---------|---------------------------------------------------------------------------------------------------------------------------------|
+| `>` | write `stdout` to a new file; overwrites any file with that name (e.g., `ls *.md > mardkownfiles.txt`) |
+| `>>` | append `stdout` to a previously existing file; if the file does not exist, it is created (e.g., `ls *.md >> markdownfiles.txt`) |
+| `<` | assigns the information in a file to a variable, loop, etc (e.g., `n < markdownfiles.md`) |
+
+
+
+#### b.1) How to use the output of one command as the input to another with a pipe...
+A special kind of redirection is called a pipe and is denoted by `|`.
+
+
+| Command | Description |
+|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------|
+| | | Output from one command line program can be used as input to another one (e.g. ls \*.md | head gives you the first 5 `*.md` files in your directory) |
+
+
+
+
+
+##### Example:
+
+ ls *.md | head | sed -i `s/markdown/software/g`
+
+changes all the instances of the word `markdown` to `software` in the first 5 `*.md` files in your current directory.
+
+
+
+
+## 4. How to repeat operations using a loop...
+Loops assign a value in a list or counter to a variable that takes on a different value each time through the loop.
+There are 2 primary kinds of loops: `for` loops and `while` loops.
+
+### a) For loop
+For loops loop through variables in a list
+
+
+ for varname in list
+ do
+ command 1
+ command 2
+ done
+
+where,
+
+* `for`, `in`, `do`, and `done` are keywords
+* `list` contains a list of values separated by spaces. e.g. `list` can be replaced by `1 2 3 4 5 6` or by `Bob Mary Sue Greg`. `list` can also be a variable:
+
+--
+
+ list[0]=Sam
+ list[1]=Lynne
+ list[2]=Dhavide
+ list[3]=Trevor
+ .
+ .
+ .
+ list[n]=Mark
+
+which is referenced in the loop by:
+
+ for varname in ${list[@]}
+ do
+ command 1
+ command 2
+ done
+
+
+_Note:_ Bash is zero indexed, so counting always starts at `0`, not `1`.
+
+
+### b) While Loop
+While loops loop through the commands until a condition is met. For example
+
+ COUNTER=0
+ while [ ${COUNTER} -lt 10 ]; do
+ command 1
+ command 2
+ COUNTER=`expr ${COUNTER} + 1`
+ done
+
+continues the loop as long as the value in the variable COUNTER is less than 10 (incremented by 1 on each iteration of the loop).
+
+* `while`, `do`, and `done` are keywords
+
+
+#### b.1) Commonly used conditional operators
+
+| Operator | Definition |
+|----------|--------------------------|
+| `-eq` | is equal to |
+| `-ne` | is not equal to |
+| `-gt` | greater than |
+| `-ge` | greater than or equal to |
+| `-lt` | less than |
+| `-le` | less than or equal to |
+
+Use `man bash` or `man test` to learn about other operators you can use.
+
+
+
+## 6. Finding Things
+### a) How to select lines matching patterns in text files...
+To find information within files, you use a command called `grep`.
+
+| Example command | Description |
+|--------------------------------|------------------------------------------------------------------------------------------------|
+| `grep [options] day haiku.txt` | finds every instance of the string `day` in the file haiku.txt and pipes it to standard output | |
+
+#### a.1) Commonly used `grep` options
+
+| | `grep` options |
+|------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `-E` | tells grep you will be using a regular expression. Enclose the regular expression in quotes. _Note:_ the power of `grep` comes from using regular expressions. Please see the regular expressions sheet for examples |
+| `-i` | makes matching case-insensitive |
+| `-n` | limits the number of lines that match to the first n matches |
+| `-v` | shows lines that do not match the pattern (inverts the match) |
+| `-w` | outputs instances where the pattern is a whole word |
+
+### b) How to find files with certain properties...
+To find file and directory names, you use a command called `find`
+
+| Example command | Description |
+|------------------|-------------|
+| `find . -type d` | `find` recursively descends the directory tree for each path listed to match the expression given in the command line with file or directory names in the search path |
+
+
+#### b.1) Commonly used `find` options
+
+| | `find` options |
+|---------------|---------------------------------------------------------------------------------------------------------------------------------------------------------|
+| `-type [df]` | `d` lists directories; `f` lists files |
+| `-maxdepth n` | `find` automatically searches subdirectories. If you don't want that, specify the number of levels below the working directory you would like to search |
+| `-mindepth n` | starts `find`'s search `n` levels below the working directory |
+
+
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