David, do you have any idea why ksh93 doesn't use POSIX order in the example below?
Ced ---------- Forwarded message ---------- From: Dan Douglas <[email protected]> Date: 9 January 2013 20:00 Subject: Reverse redirection / assignment order To: [email protected] When expanding simple commands, steps 3 and 4 are reversed unconditionally for all command types and number of words expanded, even in POSIX mode. http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_01 The exceptions allowed by POSIX appear to only apply to ksh93. Other shells always use the POSIX order, except Bash, which never uses the POSIX order, though the manpage description is the same as POSIX. #!/usr/bin/env bash # 1) no command expanded, 2) special builtin, 3) regular builtin. tst() { "$sh" -c 'x=$(printf 2 >&2) ${1+"$1"} <&0$(printf 1 >&2)' _ "$@" } 2>&1 for sh in {,{b,d}a,po,{,m}k,z}sh bb; do printf '%-4s: %s %s %s\n' "$sh" "$(tst)" "$(tst :)" "$(tst true)" done Out: sh : 21 21 21 # bash posix mode bash: 21 21 21 # normal mode ksh : 21 21 12 # ksh93 is the other oddball shell dash: 12 12 12 # ... ... # Everything else same as dash I don't know why this order was chosen or what the advantages to one over the other might be. -- Dan Douglas -- Cedric Blancher <[email protected]> Institute Pasteur
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