Shell Reference
Basics
. |
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 print working directory) |
history |
lists previous commands you have entered. history | less lets you page through the list. |
man cmd |
displays the manual page for a command. |
Creating and Deleting
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 |
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. |
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 |
Wildcards
* |
zero or more characters |
? |
exactly one character |
[abcde] |
exactly one of the characters listed |
[a-e] |
exactly one character in the given range |
{software,carpentry} |
exactly one entire word from the options given |
Pipes and Redirection
> |
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) |
| | | 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) |
Matching Lines
grep [options] day haiku.txt |
finds every instance of the string day in the file haiku.txt and pipes it to standard output |
-E |
tells grep you will be using a regular expression. Enclose the regular expression in quotes. |
-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 |
Finding Files
find start [options] [commands] |
look for files or directories with specified properties and take specified actions |
-type d |
match directories |
-type f |
match files |
-name 'pattern' |
match things with specific names |
-maxdepth n |
maximum search depth |
-mindepth n |
minimum search depth |
-print |
print matches |
Repeat Operations
for filename in *.txt
do
head -5 $(filename) | sort | uniq -c
done
Save Recent Commands
history | tail -20 > recent-commands.sh