Effect of Spawning COMMAND.COM on the Environment (68927)
The information in this article applies to:
- Microsoft MS-DOS operating system 3.1
- Microsoft MS-DOS operating system 3.2
- Microsoft MS-DOS operating system 3.21
- Microsoft MS-DOS operating system 3.3
- Microsoft MS-DOS operating system 3.3a
- Microsoft MS-DOS operating system 4.0
- Microsoft MS-DOS operating system 4.01
- Microsoft MS-DOS operating system 5.0
- Microsoft MS-DOS operating system 5.0a
- Microsoft MS-DOS operating system 6.0
- Microsoft MS-DOS operating system 6.2
- Microsoft MS-DOS operating system 6.21
- Microsoft MS-DOS operating system 6.22
This article was previously published under Q68927 SUMMARY
If you spawn another COMMAND.COM, the child COMMAND.COM has its own
environment space allocated to it. The size of this environment space is at
least the minimum environment size of 160 bytes. If you start the child
COMMAND.COM with the /e:<size> switch, the child's environment space is
equal to the indicated <size> in bytes, rounded up to the nearest 16-byte
boundary. The maximum allowable environment size is 32,768 bytes.
A copy of the parent process's environment variables are placed in the
child's environment space. If the parent's environment variables exceed the
space allocated to the child, the child's environment space is
automatically increased to allow for the parent's variables. Once again,
the environment space is rounded up to the nearest 16-byte boundary. Any
changes made to the child's environment have no effect on the parent's
environment.
MORE INFORMATION
By using the /e:<size> switch on COMMAND.COM, you can force the allocation
of that much memory to the environment. In MS-DOS versions 5.0 and later, a
default environment space of 256 bytes is allocated if no /e switch is used
(lesser amounts can be specified using the /e:<size> switch). In earlier
MS-DOS versions, 160 bytes is the default. The environment can grow beyond
the allocated size, but this can occur only if there is free (unallocated)
memory available that is contiguous to the currently allocated environment
block.
| Modification Type: | Major | Last Reviewed: | 5/12/2003 |
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| Keywords: | KB68927 |
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