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cde/src/cmd
Martijn Dekker 95d695cb5a Improve and document fast filescan loops (SHOPT_FILESCAN)
From README:

FILESCAN on  Experimental option that allows fast reading of files
             using while < file;do ...; done and allowing fields in
             each line to be accessed as positional parameters.

As SHOPT_FILESCAN has been enabled by default since ksh 93l
2001-06-01, the filescan loop is now documented in the manual page
and the compile-time option is no longer considered experimental.

We must disable this at runtime if --posix is active because it
breaks a portable use case: POSIXly, 'while <file; do stuff; done'
repeatedly excutes 'stuff' while 'file' can successfully be opened
for reading, without actually reading from 'file'.

This also backports a bugfix from the 93v- beta. Reproducer:

$ echo 'one two three' >foo
$ while <foo; do printf '[%s] ' "$@"; echo; done
[one two three]

Expected output:
[one] [two] [three]

The bug is that "$@" acts like "$*", joining all the positional
parameters into one word though it should be generating one word
for each.

src/cmd/ksh93/sh/macro.c: varsub():
- Backport fix for the bug described above. I do not understand the
  opaque macro.c code well enough yet to usefully describe the fix.

src/cmd/ksh93/sh/xec.c: sh_exec():
- Improved sanity check for filescan loop: do not recognise it if
  the simple command includes variable assignments, more than one
  redirection, or an output or append redirection.
- Disable filescan loops if --posix is active.
- Another 93v- fix: handle interrupts (errno==EINTR) when closing
  the input file.
2022-02-17 19:43:36 +00:00
..
builtin iffe: really abort on output{ fail (re: e20c0c6b, e72543a, b6bd981) 2022-01-01 02:28:27 +00:00
INIT Update copyright years in files changed since 1st Jan 2022 2022-01-30 20:49:04 +00:00
ksh93 Improve and document fast filescan loops (SHOPT_FILESCAN) 2022-02-17 19:43:36 +00:00
Mamfile **/Mamfile: add header comment pointing to MAM docs (re: 6cc2f6a0) 2021-01-25 14:38:58 +00:00