diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/Zsh/expn.yo | 44 |
1 files changed, 38 insertions, 6 deletions
diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo index f87832e75..5be40bf25 100644 --- a/Doc/Zsh/expn.yo +++ b/Doc/Zsh/expn.yo @@ -1881,23 +1881,55 @@ sect(Command Substitution) cindex(command substitution) cindex(substitution, command) A command enclosed in parentheses preceded by a dollar sign, like -`tt($LPAR())...tt(RPAR())', or quoted with grave -accents, like `tt(`)...tt(`)', is replaced with its standard output, with -any trailing newlines deleted. -If the substitution is not enclosed in double quotes, the -output is broken into words using the tt(IFS) parameter. +`tt($LPAR())...tt(RPAR())', or quoted with grave accents, like +`tt(`)...tt(`)', is executed in a subshell and replaced by its +standard output, with any trailing newlines deleted. If the +substitution is not enclosed in double quotes, the output is broken +into words using the tt(IFS) parameter. vindex(IFS, use of) The substitution `tt($LPAR()cat) var(foo)tt(RPAR())' may be replaced by the faster `tt($LPAR()<)var(foo)tt(RPAR())'. In this case var(foo) undergoes single word shell expansions (em(parameter expansion), em(command substitution) and em(arithmetic expansion)), but not -filename generation. +filename generation. No subshell is created. If the option tt(GLOB_SUBST) is set, the result of any unquoted command substitution, including the special form just mentioned, is eligible for filename generation. +A command with a leading pipe character, enclosed in braces prefixed by +a dollar sign, as in `tt(${|)...tt(})', is executed in the current shell +context, rather than in a subshell, and is replaced by the value of the +parameter tt(REPLY) at the end of the command. There em(must not) be +any whitespace between the opening brace and the pipe character. Any +prior value of tt($REPLY) is saved and restored around this substitution, +in the manner of a function local parameter. Other parameters declared +within the substitution also behave as locals, as if in a function, +unless `tt(typeset -g)' is used. Trailing newlines are em(not) deleted +from the final replacement in this case, and it is subject to filename +generation in the same way as `tt($LPAR())...tt(RPAR())' but is em(not) +split on tt(IFS) unless the tt(SH_WORD_SPLIT) option is set. + +Substitutions of the form `tt(${|)var(param)tt(|)...tt(})' are similar, +except that the substitution is replaced by the value of the parameter +named by var(param). No implicit save or restore applies to var(param) +except as noted for tt(REPLY), and var(param) should em(not) be declared +within the command. If var(param) names an array, array expansion rules +apply. + +A command enclosed in braces preceded by a dollar sign, and set off from +the braces by whitespace, like `tt(${ )...tt( })', is replaced by its +standard output. Like `tt(${|)...tt(})' and unlike +`tt($LPAR())...tt(RPAR())', the command executes in the current shell +context with function local behaviors and does not create a subshell. + +Note that because the `tt(${|)...tt(})' and `tt(${ )...tt( })' forms +must be parsed at once as both string tokens and commands, all other +braces (`tt({)' or `tt(})') within the command either must be quoted, +or must appear in syntactically valid pairs, such as around complex +commands, function bodies, or parameter references. + texinode(Arithmetic Expansion)(Brace Expansion)(Command Substitution)(Expansion) sect(Arithmetic Expansion) cindex(arithmetic expansion) |