Q11867: C_FILE_INFO in Environment of Child Process

Article: Q11867
Product(s): See article
Version(s): 3.00 4.00 5.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | TAR55563 | mspl13_c
Last Modified: 25-AUG-1989

When you shell from a C program (spawn a process), the environment
will appear to become corrupted with a ;C_FILE_INFO (or _C_FILE_INFO)
string. (Version 5.10 uses an underscore rather than a semicolon.)

When a process is spawned, the C run time passes information about
open files to the child by inserting the identifier ";C_FILE_INFO" (or
"_C_FILE_INFO" -- no quotation marks in either case), followed by up
to 20 bytes, into the environment. During start-up, the C run time
reads the identifier, uses the information passed, and removes it from
the environment.

System() is implemented by spawning COMMAND.COM, and since COMMAND.COM
is not a C program, ";C_FILE_INFO" (or "_C_FILE_INFO") gets left in
the environment.

This behavior is harmless. The leading ";" (or "_") prevents any
collision with user-entered environment variables.

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