Call PROGRAM synchronously in separate process.
The remaining arguments are optional.
The program's input comes from file INFILE (nil means `/dev/null').
Insert output in BUFFER before point; t means current buffer; nil for BUFFER
 means discard it; 0 means discard and don't wait; and `(:file FILE)', where
 FILE is a file name string, means that it should be written to that file
 (if the file already exists it is overwritten).
BUFFER can also have the form (REAL-BUFFER STDERR-FILE); in that case,
REAL-BUFFER says what to do with standard output, as above,
while STDERR-FILE says what to do with standard error in the child.
STDERR-FILE may be nil (discard standard error output),
t (mix it with ordinary output), or a file name string.

Fourth arg DISPLAY non-nil means redisplay buffer as output is inserted.
Remaining arguments are strings passed as command arguments to PROGRAM.

If executable PROGRAM can't be found as an executable, `call-process'
signals a Lisp error.  `call-process' reports errors in execution of
the program only through its return and output.

If BUFFER is 0, `call-process' returns immediately with value nil.
Otherwise it waits for PROGRAM to terminate
and returns a numeric exit status or a signal description string.
If you quit, the process is killed with SIGINT, or SIGKILL if you quit again.

Send text from START to END to a synchronous process running PROGRAM.
The remaining arguments are optional.
Delete the text if fourth arg DELETE is non-nil.

Insert output in BUFFER before point; t means current buffer; nil for
 BUFFER means discard it; 0 means discard and don't wait; and `(:file
 FILE)', where FILE is a file name string, means that it should be
 written to that file (if the file already exists it is overwritten).
BUFFER can also have the form (REAL-BUFFER STDERR-FILE); in that case,
REAL-BUFFER says what to do with standard output, as above,
while STDERR-FILE says what to do with standard error in the child.
STDERR-FILE may be nil (discard standard error output),
t (mix it with ordinary output), or a file name string.

Sixth arg DISPLAY non-nil means redisplay buffer as output is inserted.
Remaining args are passed to PROGRAM at startup as command args.

If BUFFER is 0, `call-process-region' returns immediately with value nil.
Otherwise it waits for PROGRAM to terminate
and returns a numeric exit status or a signal description string.
If you quit, the process is killed with SIGINT, or SIGKILL if you quit again.

Get the value of environment variable VARIABLE.
VARIABLE should be a string.  Value is nil if VARIABLE is undefined in
the environment.  Otherwise, value is a string.

This function searches `process-environment' for VARIABLE.

If optional parameter ENV is a list, then search this list instead of
`process-environment', and return t when encountering a negative entry
(an entry for a variable with no value).