Environment variables are a set of dynamic named values that can affect the way running processes will behave on a computer.
They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP environment variable to discover a suitable location to store temporary files, or the HOME or USERPROFILE variable to find the directory structure owned by the user running the process.
They were introduced in their modern form in 1979 with Version 7 Unix, so are included in all Unix operating system flavors and variants from that point onward including Linux and OS X. From PC DOS 2.0 in 1982, all succeeding Microsoft operating systems including Microsoft Windows, and OS/2 also have included them as a feature, although with somewhat different syntax, usage and standard variable names.
In all Unix and Unix-like systems, each process has its own separate set of environment variables. By default, when a process is created, it inherits a duplicate environment of its parent process, except for explicit changes made by the parent when it creates the child. At the API level, these changes must be done between running fork
and exec
. Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env
or using the ENVIRONMENT_VARIABLE=VALUE <command>
notation. All Unix operating system flavors, DOS, and Windows have environment variables; however, they do not all use the same variable names. A running program can access the values of environment variables for configuration purposes.
CLS may refer to:
In computing, CLS
(for clear screen) is a command used by the command line interpreters COMMAND.COM and CMD.EXE on DOS, OS/2 and Microsoft Windows operating systems to clear the screen or console window of commands and any output generated by them. It does not clear the user's history of commands, however. The command is also available in the DEC RT-11 operating system. In other environments, such as Linux and Unix, the same functionality is provided by the clear command.
While the ultimate origins of using the three-character string CLS as the command to clear the screen likely predate Microsoft's use, this command was present before its MS-DOS usage, in the embedded ROM BASIC dialects Microsoft wrote for early 8-bit microcomputers (such as TRS-80 Color BASIC), where it served the same purpose. The MS-DOS dialects of BASIC written by Microsoft, BASICA and GW-BASIC, also have the CLS command as a BASIC keyword - as do various non-Microsoft implementations of BASIC such as BBC BASIC found on the BBC Micro computers. The CLS command is also present in BASIC versions for Microsoft Windows, however this generally clears text printed on the form, rather than the whole screen or controls on the form.
We are young we can break
Watch us fall
We can take some train
Down to the sea
We are glass, we are glass
We are real you can touch
Just for now
And then say
'Hey you, which way is down'
We are glass, we are glass
We are strong we run though
We have time
And to you I'm just
One of those boys
We are glass, we are glass
We are cold
We're not supposed to cry
But it's all just a thought
So here am I
We are glass, we are glass
They run fast
Impressions of the floors inviting
Stay with me, stay with me
They run past
With telephones they scream
Well would you turn all this down
Turn all this down
You are replaced you are you
And our dreams are real
And dreams are all we need
We are glass, we are glass
We slip down
And old eyes don't cry for me
Cause I doubt I'm and I doubt you
And never never going to doubt
We are glass, we are glass
They run fast
Impressions of the floors inviting
Stay with me, stay with me
They run past
With telephones they scream
Well would you turn all this down
Turn all this down