From Newsgroup: comp.lang.awk

The topic for today is: What can we get away with for clause 3 of a "for" statement.

Observe (notice that the print statement is *inside* the for statement):

First, we use a print statement as clause 3:
% gawk4 'BEGIN { for (i=1; i<=5; print "i =",i++); }'
i = 1
i = 2
i = 3
i = 4
i = 5

But here we show that print really is a statement and not an expression:
% gawk4 'BEGIN { print (print "help") }'
gawk4: cmd. line:1: BEGIN { print (print "help") }
gawk4: cmd. line:1: ^ syntax error
%
(You get the same error with or without the parens)

Now, the point here is that I always thought that clause 3 in a for
statement had to be an expression (like clauses 1 and 2). But it seems we
can get away with having a statement there - if it is simple enough.

Note that in C, there's no real distinction between a simple statement and
an expression; for example, printf() is usually used as if it was a
statement, but it is in fact a function that returns a value, i.e., an expression. So, in C, clause 3 of the for statement is usually thought of
as a statement, but is, in fact, an expression.

Next, we press our luck:

This works:
% gawk4 'BEGIN { for (i=1; i<=5;) if (i++ == 3) print "three" }'
three
%

But this doesn't:
% gawk4 'BEGIN { for (i=1; i<=5; if (i++ == 3) print "three"); }'
gawk4: cmd. line:1: BEGIN { for (i=1; i<=5; if (i++ == 3) print "three"); } gawk4: cmd. line:1: ^ syntax error
gawk4: cmd. line:1: BEGIN { for (i=1; i<=5; if (i++ == 3) print "three"); } gawk4: cmd. line:1: ^ syntax error
%

Why not?
--
You are again heaping damnation upon your own head by your statements.

- Rick C Hodgin -

--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.awk

On 2025-10-03, Kenny McCormack <[email protected]> wrote:

The topic for today is: What can we get away with for clause 3 of a "for" statement.

Observe (notice that the print statement is *inside* the for statement):

First, we use a print statement as clause 3:
% gawk4 'BEGIN { for (i=1; i<=5; print "i =",i++); }'
i = 1
i = 2
i = 3
i = 4
i = 5

That's interesting, and useless; yet, stupidly, you cannot have comma expressions like for (i = 0, j = 0; ...

What you found is not portable:

$ mawk 'BEGIN { for (i=1; i<=5; print "i =",i++); }'
mawk: line 1: syntax error at or near print
--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @[email protected]
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.lang.awk

In article <[email protected]>,
Kaz Kylheku <[email protected]> wrote:

On 2025-10-03, Kenny McCormack <[email protected]> wrote:

The topic for today is: What can we get away with for clause 3 of a "for"
statement.

Observe (notice that the print statement is *inside* the for statement):

First, we use a print statement as clause 3:
% gawk4 'BEGIN { for (i=1; i<=5; print "i =",i++); }'
i = 1
i = 2
i = 3
i = 4
i = 5

That's interesting, and useless; yet, stupidly, you cannot have comma >expressions like for (i = 0, j = 0; ...

TAWK allows that syntax, but only in the "for" statement. It doesn't allow
it as a general expression (outside of "for"), like C does.

What you found is not portable:

I'm not surprised. I was just amazed it works at all.
--
Which of these is the crazier bit of right wing lunacy?
1) We've just had another mass shooting; now is not the time to be talking about gun control.

2) We've just had a massive hurricane; now is not the time to be talking about climate change.
--- Synchronet 3.21a-Linux NewsLink 1.2