diff options
Diffstat (limited to 'Doc/Zsh/redirect.yo')
| -rw-r--r-- | Doc/Zsh/redirect.yo | 90 |
1 files changed, 66 insertions, 24 deletions
diff --git a/Doc/Zsh/redirect.yo b/Doc/Zsh/redirect.yo index 8955e67ac..70085a5d2 100644 --- a/Doc/Zsh/redirect.yo +++ b/Doc/Zsh/redirect.yo @@ -16,7 +16,7 @@ input/output specifications. The following may appear anywhere in a simple command or may precede or follow a complex command. -Substitution occurs before var(word) or var(digit) +Expansion occurs before var(word) or var(digit) is used except as noted below. If the result of substitution on var(word) produces more than one filename, @@ -57,7 +57,7 @@ exist, even if tt(CLOBBER) is unset. item(tt(<<)[tt(-)] var(word))( The shell input is read up to a line that is the same as var(word), or to an end-of-file. -No parameter substitution, command substitution or +No parameter expansion, command substitution or filename generation is performed on var(word). The resulting document, called a em(here-document), becomes the standard input. @@ -77,10 +77,10 @@ item(tt(<<<) var(word))( Perform shell expansion on var(word) and pass the result to standard input. This is known as a em(here-string). ) -xitem(tt(<&) var(digit)) -item(tt(>&) var(digit))( +xitem(tt(<&) var(number)) +item(tt(>&) var(number))( The standard input/output is duplicated from file descriptor -var(digit) (see manref(dup)(2)). +var(number) (see manref(dup2)(2)). ) xitem(tt(<& -)) item(tt(>& -))( @@ -90,11 +90,33 @@ xitem(tt(<& p)) item(tt(>& p))( The input/output from/to the coprocess is moved to the standard input/output. ) -item(tt(>&) var(word))( -Same as `tt(>) var(word) tt(2>&1)'. +xitem(tt(>&) var(word)) +item(tt(&>) var(word))( +(Except where `tt(>&) var(word)' matches one of the above syntaxes; +`tt(&>)' can always be used to avoid this ambiguity.) +Redirects both standard output and standard error (file descriptor 2) +in the manner of `tt(>) var(word)'. +Note that this does em(not) have the same effect as `tt(>) var(word) tt(2>&1)' +in the presence of multios (see the section below). ) -item(tt(>>&) var(word))( -Same as `tt(>>) var(word) tt(2>&1)'. +xitem(tt(>&|) var(word)) +xitem(tt(>&!) var(word)) +xitem(tt(&>|) var(word)) +item(tt(&>!) var(word))( +Redirects both standard output and standard error (file descriptor 2) +in the manner of `tt(>|) var(word)'. +) +xitem(tt(>>&) var(word)) +item(tt(&>>) var(word))( +Redirects both standard output and standard error (file descriptor 2) +in the manner of `tt(>>) var(word)'. +) +xitem(tt(>>&|) var(word)) +xitem(tt(>>&!) var(word)) +xitem(tt(&>>|) var(word)) +item(tt(&>>!) var(word))( +Redirects both standard output and standard error (file descriptor 2) +in the manner of `tt(>>|) var(word)'. ) enditem() @@ -107,7 +129,7 @@ The shell evaluates each redirection in terms of the association at the time of evaluation. For example: -nofill(... tt(1>)var(fname) tt(2>&1)) +indent(... tt(1>)var(fname) tt(2>&1)) first associates file descriptor 1 with file var(fname). It then associates file descriptor 2 with the file associated with file @@ -123,12 +145,12 @@ the shell opens the file descriptor as a pipe to a process that copies its input to all the specified outputs, similar to bf(tee), provided the tt(MULTIOS) option is set. Thus: -nofill(tt(date >foo >bar)) +example(date >foo >bar) writes the date to two files, named `tt(foo)' and `tt(bar)'. Note that a pipe is an implicit redirection; thus -nofill(tt(date >foo | cat)) +example(date >foo | cat) writes the date to the file `tt(foo)', and also pipes it to cat. @@ -136,14 +158,14 @@ If the tt(MULTIOS) option is set, the word after a redirection operator is also subjected to filename generation (globbing). Thus -nofill(tt(: > *)) +example(: > *) will truncate all files in the current directory, assuming there's at least one. (Without the tt(MULTIOS) option, it would create an empty file called `tt(*)'.) Similarly, you can do -nofill(tt(echo exit 0 >> *.sh)) +example(echo exit 0 >> *.sh) If the user tries to open a file descriptor for reading more than once, the shell opens the file descriptor as a pipe to a process that copies @@ -151,17 +173,17 @@ all the specified inputs to its output in the order specified, similar to bf(cat), provided the tt(MULTIOS) option is set. Thus -nofill(tt(sort <foo <fubar)) +example(sort <foo <fubar) or even -nofill(tt(sort <f{oo,ubar})) +example(sort <f{oo,ubar}) is equivalent to `tt(cat foo fubar | sort)'. Note that a pipe is an implicit redirection; thus -nofill(tt(cat bar | sort <foo)) +example(cat bar | sort <foo) is equivalent to `tt(cat bar foo | sort)' (note the order of the inputs). @@ -169,15 +191,35 @@ If the tt(MULTIOS) option is em(un)set, each redirection replaces the previous redirection for that file descriptor. However, all files redirected to are actually opened, so -nofill(tt(echo foo > bar > baz)) +example(echo foo > bar > baz) when tt(MULTIOS) is unset will truncate bar, and write `tt(foo)' into baz. -If a simple command consists of one or more redirection operators -and zero or more parameter assignments, but no command name, -the command named in the shell variable tt(READNULLCMD) is assumed. -(If tt(READNULLCMD) is empty or not set, `tt(cat)' is used.) Thus +sect(Redirections with no command) +vindex(NULLCMD, use of) +vindex(READNULLCMD, use of) +pindex(CSH_NULLCMD, use of) +pindex(SH_NULLCMD, use of) +When a simple command consists of one or more redirection operators +and zero or more parameter assignments, but no command name, zsh can +behave in several ways. + +If the parameter tt(NULLCMD) is not set or the option tt(CSH_NULLCMD) is +set, an error is caused. This is the bf(csh) behavior and tt(CSH_NULLCMD) +is set by default when emulating bf(csh). + +If the option tt(SH_NULLCMD) is set, the builtin `tt(:)' is inserted as a +command with the given redirections. This is the default when emulating +bf(sh) or bf(ksh). + +Otherwise, if the parameter tt(NULLCMD) is set, its value will be used as a +command with the given redirections. If both tt(NULLCMD) and +tt(READNULLCMD) are set, then the value of the latter will be used instead +of that of the former when the redirection is an input. The default for +tt(NULLCMD) is `tt(cat)' and for tt(READNULLCMD) is `tt(more)'. Thus + +example(< file) -nofill(tt(< file)) +shows the contents of tt(file) on standard output, with paging if that is a +terminal. tt(NULLCMD) and tt(READNULLCMD) may refer to shell functions. -prints the contents of tt(file). |