Section 1: General Commands

Section 1 of the manual describes user commands and tools, for example, file manipulation tools, shells, compilers, web browsers, file and image viewers and editors, and so on.

All commands yield a status value on termination. This value can be tested (e.g., in most shells the variable $? contains the status of the last executed command) to see whether the command completed successfully. A zero exit status is conventionally used to indicate success, and a nonzero status means that the command was unsuccessful. (Details of the exit status can be found in wait(2).) A nonzero exit status can be in the range 1 to 255, and some commands use different nonzero status values to indicate the reason why the command failed.