diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/Zsh/redirect.yo | 58 |
1 files changed, 33 insertions, 25 deletions
diff --git a/Doc/Zsh/redirect.yo b/Doc/Zsh/redirect.yo index 3877b2313..67bad66ee 100644 --- a/Doc/Zsh/redirect.yo +++ b/Doc/Zsh/redirect.yo @@ -149,13 +149,33 @@ file descriptor 2 would be associated with the terminal (assuming file descriptor 1 had been) and then file descriptor 1 would be associated with file var(fname). -If instead of a digit one of the operators above is preceded by -a valid identifier enclosed in braces, the shell will open a new -file descriptor that is guaranteed to be at least 10 and set the -parameter named by the identifier to the file descriptor opened. -No whitespace is allowed between the closing brace and the redirection -character. The option tt(IGNORE_BRACES) must not be set. -For example: +The `tt(|&)' command separator described in +ifzman(em(Simple Commands & Pipelines) in zmanref(zshmisc))\ +ifnzman(noderef(Simple Commands & Pipelines)) +is a shorthand for `tt(2>&1 |)'. + +The various forms of process substitution, `tt(<LPAR())var(list)tt(RPAR())', +and `tt(=LPAR())var(list)(RPAR())' for input and +`tt(>LPAR())var(list)tt(RPAR())' for output, are often used together with +redirection. For example, if var(word) in an output redirection is of the +form `tt(>LPAR())var(list)tt(RPAR())' then the output is piped to the +command represented by var(list). See +ifzman(\ +em(Process Substitution) in zmanref(zshexpn))\ +ifnzman(\ +noderef(Process Substitution)). +sect(Opening file descriptors using parameters) +cindex(file descriptors, use with parameters) +cindex(parameters, for using file descriptors) + +When the shell is parsing arguments to a command, and the shell option +The option tt(IGNORE_BRACES) is not set, a different form of +redirection is allowed: instead of a digit before the operator +there is a valid shell identifier enclosed in braces. The shell will +open a new file descriptor that is guaranteed to be at least 10 and set +the parameter named by the identifier to the file descriptor opened. No +whitespace is allowed between the closing brace and the redirection +character. For example: indent(... {myfd}>&1) @@ -181,8 +201,12 @@ using it for allocating a file descriptor avoids the error. Note that this mechanism merely allocates or closes a file descriptor; it does not perform any redirections from or to it. It is usually convenient -to allocate a file descriptor prior to use as an argument to tt(exec). The -following shows a typical sequence of allocation, use, and closing of a +to allocate a file descriptor prior to use as an argument to tt(exec). +The syntax does not in any case work when used around complex commands +such as parenthesised subshells or loops, where the opening brace is +interpreted as part of a command list to be executed in the current shell. + +The following shows a typical sequence of allocation, use, and closing of a file descriptor: example(integer myfd @@ -194,22 +218,6 @@ Note that the expansion of the variable in the expression tt(>&$myfd) occurs at the point the redirection is opened. This is after the expansion of command arguments and after any redirections to the left on the command line have been processed. - -The `tt(|&)' command separator described in -ifzman(em(Simple Commands & Pipelines) in zmanref(zshmisc))\ -ifnzman(noderef(Simple Commands & Pipelines)) -is a shorthand for `tt(2>&1 |)'. - -The various forms of process substitution, `tt(<LPAR())var(list)tt(RPAR())', -and `tt(=LPAR())var(list)(RPAR())' for input and -`tt(>LPAR())var(list)tt(RPAR())' for output, are often used together with -redirection. For example, if var(word) in an output redirection is of the -form `tt(>LPAR())var(list)tt(RPAR())' then the output is piped to the -command represented by var(list). See -ifzman(\ -em(Process Substitution) in zmanref(zshexpn))\ -ifnzman(\ -noderef(Process Substitution)). sect(Multios) cindex(multios) pindex(MULTIOS, use of) |