1 Signal Description 2 the HUP ( 1 ) # pending, commonly due to dropped or user terminal quits initiator . 3 the INT ( 2 ) # interrupted, usually by pressing the + the Ctrl C key combination initiated . 4 the QUIT ( . 3 ) # exit, typically by + pressing the Ctrl \ key combination caused . 5 ABRT ( . 6 ) # suspension, typically performed for some serious error caused . 6 ALRM ( 14 ) # alarm, usually for processing a timeout . 7 the TERM ( 15 ) # terminates, the system typically sending shutdown . 8 . 9 Trap after capture signal, there are three ways the reaction: 10 . 1 , the implementation of a program to process the signals . 11 2 , accept the default action signal 12 is . 3 , ignore this signal 13 is 14 The first form of the shell trap command is received numerical signal list manifest the same signal, the execution command string in double quotes: 15 trap ' Commands ' Signal- List # single quotation marks, to detect the signal in the shell when it carries out replacement for commands and variables, time has changed 16 Trap " commands " replacement signal-list # double quotes, shell for the first time when he set the signal execute commands and variables, time-invariant