Command Line Crib Sheet

Commands, Special Symbols, and Keyboard Shortcuts

!	exclamation point/bang	Shortcut for repeating a command—!<command number> repeats the command with that number (as listed by the history command); !! repeats the last command
/	forward slash	Separates successive folders in a cd command
<	input redirect/less-than sign	Specifies that the content of a file (to the right of the <) should serve as the input into the command on the left
>	output redirect/greater-than sign	Specifies that the result of a program (to the left of the <) should be saved into the file on the left
	pipe	becomes the input into the program to the right
~, ~username	tilde	Shortcut for a user’s home folder; when immediately followed by a username (no spaces), this represents that user’s home folder
cat <filename>	concatenate a file (long story)	Display the contents of the given file
cd <directory or folder>	change directory	Changes the current directory/folder to the one indicated in the command
cp -i <file to copy> <destination of copy>	copy file	Copies the given file to the given destination; the -i stands for “interactive,” meaning that cp will ask permission if a file at the destination might get replaced
Ctrl-C		“Panic” key—bail out of the current program and jump back to the command line
Ctrl-D		“End input” key—ends a program when using it in “practice” mode (where you type the data that you want it to manipulate)
exit	exit	Log out of your command line session.
grep	general regular expression parser	Identifies input lines that match a certain pattern; the pattern is known as a regular expression or syntax, and some aspects of this regex notation are listed in the section below
history	history	Lists the commands you have typed so far
left/right arrow keys		Go backward/forward across current command (allowing you to edit it)
logout	logout	Log out of your command line session.
ls	list files	Display the files in the current directory; adding a -F to the command (i.e., ls -F) adds a symbol to the file listings indicating their type
mv -i <file to move or rename> <new location or name of the file>	move or rename a file	Move or rename a file; as with cp, the -i is an “interactive” mode that asks permission if something might get replaced
pwd	print working directory	Displays the directory/folder in which you are working; the command prompt also shows this
sed	stream editor	Searches (like grep) and replaces matching text with another piece of text; matches are also specified with a regex (one section below) with some text replacement options listed two sections below
Tab key	autocomplete	Lists possible matching choices if there is more than one, or autofills immediately if there is only one match
up/down arrow keys		Go back and forth through command history

Search Pattern Symbols (a.k.a. regular expression or regex symbols)

Used by grep, sed, and XMLPipeDB Match to indicate what patterns to find.

.	Single-character wildcard	Matches any character
*	Zero or more	Matches zero or more of the symbol that precedes it
^	Beginning of line	Matches the pattern after it only if it appears at the beginning of a line
$	End of line	Matches the pattern before it only if it appears at the end of a line
+	One or more	Matches one or more of the symbol that precedes it
\"	Double-quote character	Matches a double-quote in a line; the extra backslash (\) is needed so that this quote is not confused for indicating the end of the search pattern
\d	Number 0-9 (i.e., digit)	Matches any single-digit number
\w	Letter or number (i.e., something that would appear in a word)	Matches any letter or number, but not punctuation, spaces, or other symbols
[<characters>]	“Multiple choice” match	Matches any single character between the brackets
{number}	Specific number of repetitions	Matches the preceding pattern for the specific number of times; requires the addition of a -r option after sed to indicate the use of this “shortcut” notation

sed Search/Replace Directives

"s/<pattern to replace>/<replacement text>/g"	Replaces the given pattern with the given text; if the replacement text contains a &, the matched pattern will be substituted for that symbol
"y/<original characters>/<replacement characters>/"	Replace the original characters with the given replacements, following the order in which the characters are given (note there is no g at the end of this directive)
\<special character>	Enables the use of characters that otherwise have special meaning for sed (e.g., ", /) as if they were “regular” characters; can be used for both matching and replacing
number(s) preceding s or y	Makes sed perform the text replacement only for the matching line numbers; line ranges can be given as two numbers separated by a comma (,)
number instead of g at the end	Makes sed perform the text replacement only for the “number”-th match in a line (but still does this for every line)
\n	Represents a line break—when used in the replacement portion of a sed command, this breaks one line into two at the point where the matching text was found
sed ':a;N;$!ba;s/\n//g'	Highly specialized sed command for combining lines—this puts two lines together
<line number(s)>D	Deletes the lines given by the line numbers (does not touch the original file; instead, this skips the line in the result that sed produces)