Environment variable

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.

Details

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.

24 (season 1)

The first season of the American drama television series 24, also known as Day 1, was first broadcast from November 6, 2001, to May 21, 2002 on Fox. The season's storyline starts and ends at 12:00 a.m. on the day of the California presidential primary.

Season overview

The first season takes place on the day of a fictional U.S. presidential primary.

The season's main plot revolves around an assassination attempt on U.S. Senator from Maryland, David Palmer, a candidate for the Democratic Party presidential nomination, on the day of the primary in California. The central character is Jack Bauer, a former Delta Force operator who is the Director of the fictional Counter Terrorist Unit (CTU) in Los Angeles. Bauer becomes professionally as well as personally involved when his wife Teri and daughter Kim are kidnapped by the people behind the assassination plot.

The season is essentially divided into two halves:

24 (season 6)

The sixth season of the American drama television series 24, also known as Day 6, premiered in the United States on Fox on January 14, 2007, and concluded on May 21, 2007. The season's storyline begins and ends at 6:00 a.m. It is set 20 months after the events of the fifth season.

Season overview

The sixth season is set 20 months after season five. Over the last 11 weeks before Day 6, the United States has been targeted coast-to-coast in a series of suicide bombings. A man named Abu Fayed agrees to give the U.S. the location of Hamri Al-Assad, the supposed terrorist mastermind of these attacks, in exchange for former CTU Agent Jack Bauer with whom he has a personal grudge. As a result, President Wayne Palmer has negotiated the release of Bauer, who was illegally captured by Chinese government agents, under "high-price" terms.

Season 6 can be divided into two main acts: