diff options
Diffstat (limited to 'Doc/Zsh')
| -rw-r--r-- | Doc/Zsh/redirect.yo | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/Doc/Zsh/redirect.yo b/Doc/Zsh/redirect.yo index 3ce4b4369..ba4d17a55 100644 --- a/Doc/Zsh/redirect.yo +++ b/Doc/Zsh/redirect.yo @@ -174,6 +174,27 @@ parameter is readonly. However, it is not an error to read or write a file descriptor using tt(<&$)var(param) or tt(>&$)var(param) if var(param) is readonly. +If the option tt(CLOBBER) is unset, it is an error to open a file +descriptor using a parameter that is already set to an open file descriptor +previously allocated by this mechanism. Unsetting the parameter before +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 +file descriptor: + +example(integer myfd +exec {myfd}>~/logs/mylogfile.txt +print This is a log message. >&$myfd +exec {myfd}>&-) + +Note that the expansion of the variable in the expression tt(>&$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)) @@ -230,6 +251,10 @@ example(sort <f{oo,ubar}) is equivalent to `tt(cat foo fubar | sort)'. +Expansion of the redirection argument occurs at the point the redirection +is opened, at the point described above for the expansion of the variable +in tt(>&$myfd). + Note that a pipe is an implicit redirection; thus example(cat bar | sort <foo) |