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Existing codes using | and \| in POSIX BRE is non-portable. In POSIX BRE, selection by | or \| is not available. Selection \| in BRE is extension by implementations such as GNU sed. Selection is available in POSIX ERE, and POSIX sed started to support "sed -E" for ERE in POSIX.1-2024, but the standard is still new. We have been using BRE in the codebase anyway, and we have been fine with BRE. These were not detected by test/runLint because they are on lines different from "sed". References: 9b531a0 (apt-get), 334b47c (ebtables), 0ad9c24 (iptables), b33a3c5 (mplayer), 3a69bd3 (service). * Note: To confirm that "|"s used in "ebtables" indeed intend to mean selection, an example output from "ebtables" is this: ``` # ebtables -t nat -L Bridge table: nat Bridge chain: PREROUTING, entries: 0, policy: ACCEPT Bridge chain: OUTPUT, entries: 0, policy: ACCEPT Bridge chain: POSTROUTING, entries: 0, policy: ACCEPT ``` where one observes "PREROUTING", "OUTPUT", and "POSTROUTING" appear separately.
scop
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Jan 31, 2026
scop
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Jan 31, 2026
In the first place, we do not have to use "sed" to create the regular expression, and we do not have to use "sed" to filter the lines using a regular expression either.
In POSIX BRE used in sed, the character escape sequences like "\t" and "\r" and perlre(1)-origin character class "\w" cannot be used. They are GNU extensions. The only available escape sequence is "\n" in the replacement of "s///". References: 98dee7d (apt-get), 116db06 (gpg), e1f39bd (gpg2), 622abf3 (ipmitool), b7937bf (screen).
POSIX requires ";" or <newline> before "}", though GNU grep and probably other implementations are permissive when the context is unambiguous. These were introduced in commit c10a272.
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scop
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scop
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The word-boundary anchors \<\> are used in sed to exclude already specified items from a list. However, they are non-POSIX. Actually, we can use `compgen -X` to exclude items from the generated list, so we do not have to use "sed" in the first place.
Currently, in POSIX-bracket expressions [...] in the POSIX sed regular expressions, a backslash is treated literally, i.e., a single backslash is enough to include it in the set of characters. However, according to a newly added paragraph "APPLICATION USAGE/p5 - sed - POSIX Issue 8 XCU", POSIX may allow implementations to interpret backslashes in bracket expressions bracket in the future (in a similar way as POSIX awk processes). It recommends using two backslashes in bracket expressions for the future compatibility. https://pubs.opengroup.org/onlinepubs/9799919799/utilities/sed.html#tag_20_109_16
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In the current implementation, we try to filter out the elements of
"${options[@]}" that already appear in "${words[@]}". The strategy is
to generate
a. "${options[@]}" and
b. the intersect of "${words[@]}" and "${options[@]}"
in a single list and to pick up only unique elements. However, the
current implementation does not correctly generate "b. the intersect".
It also contains elements of words that contain any of "${options[@]}"
as a substring. This possibly results in generating some words in the
command line as options.
scop#1564 (comment)
In this patch, we rather implement the filtering using `_compgen -X`.
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The filtering attempted in the iptables completion have not taken effect because `s/.../.../p` (contained in "$chain") has been performed before the filtering by "s/<chains-to-remove>//". In this perspective, the ebtables completion did the correct thing by first performing the filtering and then performing `s/.../.../p`. However, even with the above issue fixed, both the iptables and ebtables completion may wrongly reduce a part of chain names, such as `DOCKER-FORWARD` to `DOCKER-`. The filtering should be done by the exact match. One solution is to split the "sed" invocation into "sed" and "grep -v" and perform the filtering of the exact match in the "grep" command as "grep -vEx 'INPUT|OUTPUT|...'". In this patch, we instead use the option `-X '@(INPUT|OUTPUT|...)'` of `_comp_compgen_split`. scop#1564 (comment) Co-authored-by: Ville Skyttä <ville.skytta@iki.fi>
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As suggested in Ref. [1]. [1] \ scop#1564 (comment)
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As suggested in Ref. [1]. [1] \ #1564 (comment)
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