intro(1) intro(1)NAME intro - introduces the command and application programs DESCRIPTION This section describes, in alphabetical order, generally available commands. Certain distinctions of purpose are made using parenthetical designations in the guide words at the top of each page: 1C Specifies commands for communication with other systems. 1G Specifies commands used primarily for graphics and computer-aided design. 1N Specifies network commands. DIAGNOSTICS Upon termination, each command returns two bytes of status, one supplied by the system and giving the cause for termination, and (in the case of ``normal'' termination) one supplied by the program (see wait(2) and exit(2)). The former byte is 0 for normal termination; the latter is customarily 0 for successful execution and nonzero to indicate troubles such as erroneous parameters, bad or inaccessible data, or other inability to cope with the task at hand. It is called variously ``exit code,'' ``exit status,'' or ``return code,'' and is described only where unusual conventions are involved. If present, this information is offered within the section entitled ``Status Messages and Values.'' WARNINGS Some commands produce unexpected results when processing files containing null characters. These commands often treat text input lines as strings and therefore become confused upon encountering a null character (the string terminator) within a line. January 1992 1