Commands, Special Symbols, and Keyboard Shortcuts
| !
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exclamation point/bang
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Shortcut for repeating a command—!<command number> repeats the command with that number (as listed by the history command); !! repeats the last command
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| /
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forward slash
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Separates successive folders in a cd command
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| <
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input redirect/less-than sign
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Specifies that the content of a file (to the right of the <) should serve as the input into the command on the left
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| >
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output redirect/greater-than sign
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Specifies that the result of a program (to the left of the <) should be saved into the file on the left
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|
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pipe
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becomes the input into the program to the right
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| ~, ~username
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tilde
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Shortcut for a user’s home folder; when immediately followed by a username (no spaces), this represents that user’s home folder
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| cat <filename>
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concatenate a file (long story)
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Display the contents of the given file
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| cd <directory or folder>
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change directory
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Changes the current directory/folder to the one indicated in the command
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| cp -i <file to copy> <destination of copy>
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copy file
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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
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| Ctrl-C
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“Panic” key—bail out of the current program and jump back to the command line
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| Ctrl-D
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“End input” key—ends a program when using it in “practice” mode (where you type the data that you want it to manipulate)
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| exit
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exit
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Log out of your command line session.
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| grep
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general regular expression parser
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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
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| history
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history
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Lists the commands you have typed so far
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| left/right arrow keys
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Go backward/forward across current command (allowing you to edit it)
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| logout
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logout
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Log out of your command line session.
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| ls
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list files
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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
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| mv -i <file to move or rename> <new location or name of the file>
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move or rename a file
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Move or rename a file; as with cp, the -i is an “interactive” mode that asks permission if something might get replaced
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| pwd
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print working directory
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Displays the directory/folder in which you are working; the command prompt also shows this
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| sed
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stream editor
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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
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| Tab key
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autocomplete
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Lists possible matching choices if there is more than one, or autofills immediately if there is only one match
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| up/down arrow keys
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Go back and forth through command history
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Search Pattern Symbols (a.k.a. regular expression or regex symbols)
Used by grep, sed, and XMLPipeDB Match to indicate what patterns to find.
| .
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Single-character wildcard
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Matches any character
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| *
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Zero or more
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Matches zero or more of the symbol that precedes it
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| ^
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Beginning of line
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Matches the pattern after it only if it appears at the beginning of a line
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| $
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End of line
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Matches the pattern before it only if it appears at the end of a line
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| +
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One or more
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Matches one or more of the symbol that precedes it
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| \"
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Double-quote character
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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
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| \d
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Number 0-9 (i.e., digit)
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Matches any single-digit number
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| \w
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Letter or number (i.e., something that would appear in a word)
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Matches any letter or number, but not punctuation, spaces, or other symbols
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| [<characters>]
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“Multiple choice” match
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Matches any single character between the brackets
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| {number}
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Specific number of repetitions
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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
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sed Search/Replace Directives
| "s/<pattern to replace>/<replacement text>/g"
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Replaces the given pattern with the given text; if the replacement text contains a &, the matched pattern will be substituted for that symbol
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| "y/<original characters>/<replacement characters>/"
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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)
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| \<special character>
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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
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| number(s) preceding s or y
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Makes sed perform the text replacement only for the matching line numbers; line ranges can be given as two numbers separated by a comma (,)
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| number instead of g at the end
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Makes sed perform the text replacement only for the “number”-th match in a line (but still does this for every line)
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| \n
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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
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| sed ':a;N;$!ba;s/\n//g'
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Highly specialized sed command for combining lines—this puts two lines together
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| <line number(s)>D
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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)
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