Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
echo
exit 0
See also Example 10−28.
The largest positive integer a function can return is 256. The return command is closely tied to
the concept of exit status, which accounts for this particular limitation. Fortunately, there are
various workarounds for those situations requiring a large integer return value from a function.
Example 23−5. Testing large return values in a function
#!/bin/bash
# return−test.sh
# The largest positive value a function can return is 256.
return_test ()
{
return $1
}
# Returns whatever passed to it.
return_test 27
# o.k.
echo $? # Returns 27.
return_test 256 # Still o.k.
echo $? # Returns 256.
return_test 257
echo $?
# Error!
# Returns 1 (return code for miscellaneous error).
return_test −151896 # However, large negative numbers work.
echo $? # Returns −151896.
exit 0
As we have seen, a function can return a large negative value. This also permits returning large
positive integer, using a bit of trickery.
An alternate method of accomplishing this is to simply assign the "return value" to a global
variable.
Return_Val=
# Global variable to hold oversize return value of function.
alt_return_test ()
{
fvar=$1
Return_Val=$fvar
return # Returns 0 (success).
}
alt_return_test 1
echo $? # 0
echo "return value = $Return_Val" # 1
Chapter 23. Functions 280