execline
Software
skarnet.org
 The background program 
background launches a command in the background, then goes on
with the execution flow.
 Interface 
 In an execlineb script:
     background [ -d ] { prog1... } prog2...
 -  background reads a prog1... command in a
block and unquotes it. 
-  It spawns a child executing prog1.... 
-  It sets the ! environment
variable to the pid of the prog1... process. 
-  It then execs into prog2.... 
 Options 
 -  -d : doublefork. If the -d option is set,
prog1... will run as a grandchild of background. 
 Notes 
 -  background prog1... "" prog2... is
equivalent to sh -c 'prog1... & ; exec prog2...'.