intro(1) intro(1)NAME intro - introduction to commands and applications programs DESCRIPTION This section describes, in alphabetical order, generally available commands. Certain distinctions of purpose are made in the headings: (1C) Commands for communication with other systems. (1G) Commands used primarily for graphics and computer- aided design. (1N) Network commands. DIAGNOSTICS Upon termination, each command returns two bytes of status, one supplied by the system and giving the cause for termina- tion, and (in the case of ``normal'' termination) one sup- plied 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 special conventions are involved. WARNINGS Some commands produce unexpected results when processing files containing null characters. These commands often treat text input lines as strings and therefore become con- fused upon encountering a null character (the string termi- nator) within a line. April, 1990 1