Drag folder to Terminal Enters pathname Up and Down Arrow keys Accesses prior commands Control-A Moves cursor to the beginning of the line Control-E Moves cursor to the end of the line Control-F Moves forward one character Control-B Moves backward one character Esc F Moves forward one word Esc B Moves backward one word.
Historically, the command line interface provided a way to manipulate a computer over simple, text-based connections. In the modern era, in spite of the ability to transmit graphical user interfaces over the Internet, the command line remains a powerful tool for performing certain types of tasks.
As described previously in Before You Begin, most users interact with a command-line environment using the Terminal application, though you may also use a remote connection method such as secure shell (SSH). Each Terminal window or SSH connection provides access to the input and output of a shell process. A shell is a special command-line tool that is designed specifically to provide text-based interactive control over other command-line tools.
In addition to running individual tools, most shells provide some means of combining multiple tools into structured programs, called shell scripts (the subject of this book).
Different shells feature slightly different capabilities and scripting syntax. Although you can use any shell of your choice, the examples in this book assume that you are using the standard OS X shell. The standard shell is
bash if you are running OS X v10.3 or later and tcsh if you are running an earlier version of the operating system.
The following sections provide some basic information and tips about using the command-line interface more effectively; they are not intended as an exhaustive reference for using the shell environments.
Note: This appendix was originally part of Mac Technology Overview.
Basic Shell Concepts
Before you start working in any shell environment, there are some basic features of shell scripting that you should understand. Some of these features are specific to OS X, but most are common to all platforms that support shell scripting.
Running Your First Command-Line Tool
In general, you run command-line tools that OS X provides by typing the name of the tool. (The syntax for running tools that you’ve added is described later in this appendix.)
For example, if you run the
ls command, by default, it lists the files in your home directory. To run this command, type ls and press Return.
Most tools also can take a number of flags (sometimes called switches). For example, you can get a “long” file listing (with additional information about every file) by typing
ls -l and pressing Return. The -l flag tells the ls command to change its default behavior.
Similarly, most tools take arguments. For example, to show a long listing of the files on your OS X desktop, type
ls -l Desktop and press Return. In that command, the word Desktop is an argument that is the name of the folder that contains the contents of your OS X desktop.
In addition, some tools have flags that take flag-specific arguments in addition to the main arguments to the tool as a whole.
Specifying Files and Directories
Most commands in the shell operate on files and directories, the locations of which are identified by paths. The directory names that make up a path are separated by forward-slash characters. For example, the Terminal program is in the
Utilities folder within the Applications folder at the top level of your hard drive. Its path is /Applications/Utilities/Terminal.app .
The shell (along with, for that matter, all other UNIX applications and tools) also has a notion of a current working directory. When you specify a filename or path that does not start with a slash, that path is assumed to be relative to this directory. For example, if you type
cat foo , the cat command prints the contents of the file foo in the current directory. You can change the current directory using the cd command.
Finally, the shell supports a number of directory names that have a special meaning.
Table A-1 lists some of the standard shortcuts used to represent specific directories in the system. Because they are based on context, these shortcuts eliminate the need to type full paths in many situations.
File and directory names traditionally include only letters, numbers, hyphens, the underscore character (
_ ), and often a period (. ) followed by a file extension that indicates the type of file (.txt , for example). Most other characters, including space characters, should be avoided because they have special meaning to the shell.
Although some OS X file systems permit the use of these other characters, including spaces, you must do one of the following:
For example, the path name
My Disk can be written as 'My Disk' , 'My Disk' , or My Disk .
Single quotes are safer than double quotes because the shell does not do any interpretation of the contents of a single-quoted string. However, double quotes are less likely to appear in a filename, making them slightly easier to use. When in doubt, use a backslash before the character in question, or two backslashes to represent a literal backslash.
For more detailed information, see Quoting Special Characters in Flow Control, Expansion, and Parsing.
Terminal Returns Not Found For Most Commands Mac Os X UpdateAccessing Files on Additional Volumes
On a typical UNIX system, the storage provided by local disk drives is presented as a single tree of files descending from a single root directory. This differs from the way the Finder presents local disk drives, which is as one or more volumes, with each volume acting as the root of its own directory hierarchy. To satisfy both worlds, OS X includes a hidden directory,
Volumes , at the root of the local file system. This directory contains all of the volumes attached to the local computer.
To access the contents of other local (and many network) volumes, you prefix the volume-relative path with
/Volumes/ followed by the volume name. For example, to access the Applications directory on a volume named MacOSX , you would use the path /Volumes/MacOSX/Applications .
Note: To access files on the boot volume, you are not required to add volume information, since the root directory of the boot volume is
/ . Including the volume information still works, though, so if you are interacting with the shell from an application that is volume-aware, you may want to add it, if only to be consistent with the way you access other volumes. You must include the volume information for all volumes other than the boot volume.
Input And Output
Most tools take text input from the user and print text out to the user’s screen. They do so using three standard file descriptors, which are created by the shell and are inherited by the program automatically. These standard file descriptors are listed in Table A-2.
To learn more about working with these descriptors, including redirecting the output of one tool to the input of another, read Shell Input and Output.
Terminating Programs
To terminate the currently running program from the command line, press Control-C. This keyboard shortcut sends an abort (
ABRT ) signal to the currently running process. In most cases this causes the process to terminate, although some tools may install signal handlers to trap this signal and respond differently. (See Trapping Signals in Advanced Techniques for details.)
In addition, you can terminate most scripts and command-line tools by closing a Terminal window or SSH connection. This sends a hangup (
HUP ) signal to the shell, which it then passes on to the currently running program. If you want a program to continue running after you log out, you should run it using the nohup command, which catches that signal and does not pass it on to whatever command it invokes.
Frequently Used Commands
Shell scripting involves a mixture of built-in shell commands and standard programs that run in all shells. Although most shells offer the same basic set of commands, there are often variations in the syntax and behavior of those commands. In addition to the shell commands, OS X also provides a set of standard programs that run in all shells.
Table A-3 lists some commands that are commonly used interactively in the shell. Most of the items in this table are not specific to any given shell. For syntax and usage information for each command, see the corresponding man page. For a more in-depth list of commands and their accompanying documentation, see OS X Man Pages.
Environment Variables
Some programs require the use of environment variables for their execution. Environment variables are variables inherited by all programs executed in the shell’s context. The shell itself uses environment variables to store information such as the name of the current user, the name of the host computer, and the paths to any executable programs. You can also create environment variables and use them to control the behavior of your program without modifying the program itself. For example, you might use an environment variable to tell your program to print debug information to the console.
To set the value of an environment variable, you use the appropriate shell command to associate a variable name with a value. For example, to set the environment variable
MYFUNCTION to the value MyGetData in the global shell environment you would type the following command in a Terminal window:
When you launch an application from a shell, the application inherits much of its parent shell’s environment, including any exported environment variables. This form of inheritance can be a useful way to configure the application dynamically. For example, your application can check for the presence (or value) of an environment variable and change its behavior accordingly. Different shells support different semantics for exporting environment variables, so see the man page for your preferred shell for further information.
Child processes of a shell inherit a copy of the environment of that shell. Shells do not share their environments with one another. Thus, variables you set in one Terminal window are not set in other Terminal windows. Once you close a Terminal window, any variables you set in that window are gone.
If you want the value of a variable to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.
Similarly, environment variables set by tools or subshells are lost when those tools or subshells exit.
Running User-Added Commands
As mentioned previously, you can run most tools by typing their name. This is because those tools are located in specific directories that the shell searches when you type the name of a command. The shell uses the
PATH environment variable to control where it searches for these tools. It contains a colon-delimited list of paths to search--/usr/bin:/bin:/usr/sbin:/sbin , for example.
If a tool is in any other directory, you must provide a path for the program to tell it where to find that tool. (For security reasons, when writing scripts, you should always specify a complete, absolute path.)
For security reasons, the current working directory is not part of the default search path (
PATH ), and should not be added to it. If it were, then another user on a multi-user system could trick you into running a command by adding a malicious tool with the same name as one you would typically run (such as the ls command) or a common misspelling thereof.
For this reason, if you need to run a tool in the current working directory, you must explicitly specify its path, either as an absolute path (starting from
/ ) or as a relative path starting with a directory name (which can be the . directory). For example, to run the MyCommandLineProgram tool in the current directory, you could type ./MyCommandLineProgram and press Return.
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With the aforementioned security caveats in mind, you can add new parts (temporarily) to the value of the
PATH environment variable by doing the following:
If you want the additional path components to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.
Running Applications
To launch an application, you can generally either:
Note: As a general rule, if you launch a GUI application from a script, you should run that script only within Terminal or another GUI application. You cannot necessarily launch an GUI application when logged in remotely (using SSH, for example). In general, doing so is possible only if you are also logged in using the OS X GUI, and in some versions of OS X, it is disallowed entirely.
Learning About Other Commands
At the command-line level, most documentation comes in the form of man pages (short for manual). Man pages provide reference information for many shell commands, programs, and POSIX-level concepts. The manual page
manpages describes the organization of manual, and the format and syntax of individual man pages.
To access a man page, type the
man command followed by the name of the thing you want to look up. For example, to look up information about the bash shell, you would type man bash . The man pages are also included in the OS X Developer Library (OS X Man Pages).
You can also search the manual pages by keyword using the
apropos command.
Note: Not all commands and programs have man pages. For a list of available man pages, look in the
/usr/share/man directory or see OS X Man Pages in the OS X Developer Library.
Most shells have a command or man page that displays the list of commands that are built into the shell (builtins). Table A-4 lists the available shells in OS X along with the ways you can access the list of builtins for the shell.
Copyright © 2003, 2014 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2014-03-10
Welcome back to Coding Corner! Today, we're going to go over some great interface and user tweaks you can execute to customize your Mac. These tricks are often simple and can help you spruce up your Mac far beyond what the System Preferences window allows.
So, without further ado, 15 great tricks you can execute in Terminal.
Tweak the Finder
Want to see hidden files, or copy Quick Look text? There are quite a few 'defaults' commands that let you alter how the Finder looks or acts.
1. Show hidden files and folders
Want to see all the hidden files and folders OS X has to offer — or you simply can't find a file you hid? Just use this command in Terminal:
defaults write com.apple.finder AppleShowAllFiles -bool TRUE killall Finder
To re-hide all your files, just change the
TRUE to FALSE .
2. View any file's contents
If you've had a file get corrupted or you suspect there's something hidden inside its package, you can force Terminal to open it. Just use the following command:
cat ~/enter/file/path
Fair warning: If you try to open a photo or pretty much any non-text document, you'll likely just see text gibberish.
3. Copy the contents of a folder from one place to another
Sure, you can Option-drag any file to a new location to make a copy of it, but if you want to simplify the process and automatically copy the entire contents of one folder to another, check out this simple Terminal trick.
ditto -V ~/original/folder/ ~/new/folder/
4. Download files outside of your browser
Have the URL to a file but don't want to use Safari, Firefox, or Chrome to download it? You can go through Terminal with the following commands:
cd ~/Downloads/ curl -O http://www.thefilename.com/thefile/url.mp3
The first command moves your current Terminal location to your Downloads folder; the second downloads it from the web to that folder.
Modifying screenshots
Want to change how your screenshots look? Here are some commands to help you do just that.
5. Change your screenshot's file format
This Terminal command lets you change the file format of your screenshots. By default, they're saved as PNGs, but you can also save them as PDFs, JPGs, and more.
defaults write com.apple.screencapture type jpg
6. Disable drop shadows on a screenshot
Here's another good one if you tend to take a lot of screenshots: This command will disable drop-shadow on your screenshots, only displaying the window you've snapped.
$ defaults write com.apple.screencapture disable-shadow -bool TRUE killall SystemUIServer
![]() 7. Create a new default name scheme for screenshots
Don't like the phrase Apple uses to save your screenshots? Traditionally, it's 'Screen Shot - [date] - [time]', but you can change 'Screen Shot' to any word you please.
defaults write com.apple.screencapture name 'New Screen Shot Name' killall SystemUIServer`
Get bored of your new name scheme? Go back to the default by typing as follows:
defaults write com.apple.screencapture name ' killall SystemUIServer
8. Change the location of your screenshots
Your screenshots, by default, save to the Desktop. But if you'd prefer they save elsewhere, it's an easy Terminal trick to make it so.
defaults write com.apple.screencapture location ~/your/location/here killall SystemUIServer
You can also drag the folder of your choice on top of the Terminal window after typing 'location' if you don't want to manually type out the file path.
System changes
If you're looking for broader OS X-level changes, these commands might help you get started.
9. Create a custom login message
Whether you want to troll your friends or add useful 'in case of loss' contact information, you can add a personalized message to your login screen with this Terminal command.
sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText 'In case of loss, call 555-555-5555.'
10. How long has my Mac been running?
Is your Mac acting sluggishly? It might be in need of a good restart. You can check to see just how long your Mac's been active by checking its uptime with this Terminal command:
uptime
11. Keep your Mac awake
If you need to prevent your Mac from going to sleep — say, you're running an extensive task, or recording your screen — there's an all-too-amusing command for that:
caffeinate
Once you enter this command, your Mac's digital eyes will be pried open and prevented from going to sleep until you end it by pressing Control-C.
If you don't want to rely on being the one to end your poor Mac's suffering, you can also create a set a number of seconds before your Mac sleeps:
caffeinate -u -t 5400
The above command will keep your Mac awake for an hour and a half.
12. Make your Mac automatically restart after a crash
We've all had our Mac freeze up or crash at least once in its lifetime. If you want to skip the crying and the yelling at the screen and get back to work, you can enter this Terminal command, which will make OS X reboot as soon as it senses a full system freeze.
sudo systemsetup -setrestartfreeze on
Terminal Returns Not Found For Most Commands Mac Os X 10 11Modify your Dock
Want to make your Dock look different? Check out these Terminal tweaks.
13. Add spacers to your Dock
You can organize your Dock's many icons by adding in blank spaces with this handy terminal command:
defaults write com.apple.dock persistent-apps -array-add '{'tile-type'='spacer-tile';}' killall Dock
Repeat this command for each spacer you'd like for your Dock. To remove a spacer, you can drag it out to the right until you see the poof icon.
Terminal Returns Not Found For Most Commands Mac Os X Versions14. Dull hidden apps in the Dock
Not sure which apps are visible on your screen? You can make this information extra pertinent by using this Terminal command, which lowers the opacity on icons for hidden apps in the Dock. It's a great way to see what you haven't used lately, as well as what's cluttering up your screen.
defaults write com.apple.Dock showhidden -bool TRUE killall Dock
15. Hide non-active apps in your DockTerminal Returns Not Found For Most Commands Mac Os X High Sierra Download
If lowering the opacity of hidden apps appeals to you, you might like this Terminal command even better: It hides any closed app from your Dock at all times.
defaults write com.apple.dock static-only -bool TRUE killall Dock
Terminal Returns Not Found For Most Commands Mac Os X 10 12Your favorites?Terminal Returns Not Found For Most Commands Mac Os X El Capitan
Have a Terminal command you love that we didn't mention? Drop it below in the comments.
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