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author | Daniel Shahaf <danielsh@apache.org> | 2020-01-12 22:29:26 +0000 |
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committer | Daniel Shahaf <danielsh@apache.org> | 2020-01-15 22:35:09 +0000 |
commit | c7bc62aa0674d3677ce019333f4b8cd95aa8d189 (patch) | |
tree | 22c0c4e88fde8d385f60c77185073c01734f59b9 /Doc/Zsh/expn.yo | |
parent | faa476a4ed1750f117d76dd8f99f0fa1849ab539 (diff) | |
download | zsh-c7bc62aa0674d3677ce019333f4b8cd95aa8d189.tar.gz zsh-c7bc62aa0674d3677ce019333f4b8cd95aa8d189.tar.xz zsh-c7bc62aa0674d3677ce019333f4b8cd95aa8d189.zip |
45287: zshexpn: Describe parameter elision and add some introductory prose
Diffstat (limited to 'Doc/Zsh/expn.yo')
-rw-r--r-- | Doc/Zsh/expn.yo | 31 |
1 files changed, 20 insertions, 11 deletions
diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo index 9451fa605..c129b4228 100644 --- a/Doc/Zsh/expn.yo +++ b/Doc/Zsh/expn.yo @@ -582,7 +582,25 @@ and subscript notation to access individual array elements. Note in particular the fact that words of unquoted parameters are not automatically split on whitespace unless the option tt(SH_WORD_SPLIT) is set; see references to this option below for more details. This is an -important difference from other shells. +important difference from other shells. However, as in other shells, +null words are elided from unquoted parameters' expansions. + +With default options, after the assignments: + +example(array=("first word" "" "third word") +scalar="only word") + +then tt($array) substitutes two words, `tt(first word)' and `tt(third +word)', and tt($scalar) substitutes a single word `tt(only word)'. Note +that second element of tt(array) was elided. Scalar parameters can +be elided too if their value is null (empty). To avoid elision, use quoting as +follows: tt("$scalar") for scalars and tt("${array[@]}") or tt("${(@)array}") +for arrays. (The last two forms are equivalent.) + +Parameter expansions can involve em(flags), as in `tt(${(@kv)aliases})', +and other operators, such as `tt(${PREFIX:-"/usr/local"})'. Parameter +expansions can also be nested. These topics will be introduced below. +The full rules are complicated and are noted at the end. In the expansions discussed below that require a pattern, the form of the pattern is the same as that used for filename generation; @@ -594,17 +612,8 @@ noderef(Modifiers) in noderef(History Expansion) can be applied: for example, tt(${i:s/foo/bar/}) performs string substitution on the expansion of parameter tt($i). -In the following descriptions, `word' refers to a single word +In the following descriptions, `var(word)' refers to a single word substituted on the command line, not necessarily a space delimited word. -With default options, after the assignments: - -example(array=("first word" "second word") -scalar="only word") - -then tt($array) substitutes two words, `tt(first word)' and `tt(second -word)', and tt($scalar) substitutes a single word `tt(only word)'. This -may be modified by explicit or implicit word-splitting, however. The -full rules are complicated and are noted at the end. startitem() item(tt(${)var(name)tt(}))( |