Intel XENIX 286 Programmers Guide (86) - Tenox.tc

XENIX Programming csh: C Shell
Note: When setting $status (as in the cmp statement above), the status will change if
anything is done between the cmp statement and the "if ($status != 0) then" statement.
For example:
cmp -s $i -/backup/$i :t # to set $status
echo $status
if ($status ! = 0) then
The other control construct is a statement of the form
if (expression) then
command
end if
# if fi les are different, status = 1
# will echo 1 , but status will be set to 0
# now status = 0, but it should be 1
The placement of the keywords in this statement is not flexible due to the current
implementation of the C shell. The following two formats are not acceptable to the C
shell:
and
if (expression) # Won't work!
then
command
end if
if (expression) then command endif # Won't work
The C shell does have another form of the if statement:
if (expression) command
which can be written
if (expression) \
command
Here we have escaped the newline for the sake of appearance. The command must not
involve "1", "&", or ";" and must not be another control command. The second form
requires the final backslash {\) to immediately precede the end-of-line.
The more general if statements above also ad mit a sequence of else-if pairs followed by
a single else and an endif, for example:
if (expression) then
commands
else if (expression) then
commands
else
end if
commands
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