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diff --git a/Doc/Zsh/grammar.yo b/Doc/Zsh/grammar.yo new file mode 100644 index 000000000..c78aed4b4 --- /dev/null +++ b/Doc/Zsh/grammar.yo @@ -0,0 +1,335 @@ +texinode(Shell Grammar)(Redirection)(Files)(Top) +chapter(Shell Grammar) +cindex(shell grammar) +cindex(grammar, shell) +startmenu() +menu(Simple Commands & Pipelines) +menu(Precommand Modifiers) +menu(Complex Commands) +menu(Alternate Forms For Complex Commands) +menu(Reserved Words) +menu(Comments) +menu(Aliasing) +menu(Quoting) +endmenu() +texinode(Simple Commands & Pipelines)(Precommand Modifiers)()(Shell Grammar) +sect(Simple Commands & Pipelines) +cindex(simple commands) +cindex(commands, simple) +A em(simple command) is a sequence of optional parameter +assignments followed by blank-separated words, +with optional redirections interspersed. +The first word is the command to be executed, and the remaining +words, if any, are arguments to the command. +If a command name is given, the parameter assignments modify +the environment of the command when it is executed. +The value of a simple command is its exit status, +or 128 plus the signal number if terminated by a signal. + +cindex(pipeline) +A em(pipeline) is either a simple command, or a sequence of two or more +simple commands where each command is separated from the next by `tt(|)' +or `tt(|&)'. Where commands are separated by `tt(|)', the standard +output of the first command is connected to the +standard input of the next. `tt(|&)' is shorthand for `tt(2>&1 |)', which +connects both the standard output and the standard error of the +command to the standard input of the next. The value of a pipeline +is the value of the last command, unless the pipeline is preceded by +`tt(!)' in which case the value is the logical inverse of the value of the +last command. + +findex(coproc) +cindex(coprocess) +If a pipeline is preceded by `tt(coproc)', it is executed as a coprocess; +a two-way pipe is established between it and the parent shell. The +shell can read from or write to the coprocess by means of the `tt(>&p)' +and `tt(<&p)' redirection operators or with `tt(print -p)' and `tt(read -p)'. +A pipeline cannot be preceded by both `tt(coproc)' and `tt(!)'. + +cindex(sublist) +A em(sublist) is either a single pipeline, or a sequence of two or more +pipelines separated by `tt(&&)' or `tt(||)'. If two pipelines are separated +by `tt(&&)', the second pipeline is executed only if the first succeeds +(returns a zero value). If two pipelines are separated by `tt(||)', the +second is executed only if the first fails (returns a nonzero value). +Both operators have equal precedence and are left associative. +The value of the sublist is the value of the last pipeline executed. + +cindex(list) +A em(list) is a sequence of zero or more sublists, in which each sublist +is terminated by `tt(;)', `tt(&)', `tt(&|)', `tt(&!)', or a newline. +This terminator +may optionally be omitted from the last sublist in the list when the +list appears as a complex command inside `tt(LPAR())...tt(RPAR())' +or `tt({)...tt(})'. When a +sublist is terminated by `tt(;)' or newline, the shell waits for it to +finish before executing the next sublist. If a sublist is terminated +by a `tt(&)', `tt(&|)', or `tt(&!)', +the shell executes it in the background, and +does not wait for it to finish. +A backgrounded sublist returns a status of zero. +texinode(Precommand Modifiers)(Complex Commands)(Simple Commands & Pipelines)(Shell Grammar) +sect(Precommand Modifiers) +cindex(precommand modifiers) +cindex(modifiers, precommand) +A simple command may be preceded by a em(precommand modifier), +which will alter how the command is interpreted. These modifiers are +shell builtin commands with the exception of tt(nocorrect) which is +a reserved word. + +startitem() +item(tt(-))( +The command is executed with a `tt(-)' prepended to its +tt(argv[0]) string. +) +item(tt(noglob))( +Filename generation (globbing) is not performed on any of +the words. +) +item(tt(nocorrect))( +Spelling correction is not done on any of the words. +) +item(tt(exec))( +The command is executed in the parent shell without forking. +) +item(tt(command))( +The command word is taken to be the name of an external command, +rather than a shell function or builtin. +) +item(tt(builtin))( +The command word is taken to be the name of a builtin command, +rather than a shell function or external command. +) +enditem() +texinode(Complex Commands)(Alternate Forms For Complex Commands)(Precommand Modifiers)(Shell Grammar) +sect(Complex Commands) +cindex(complex commands) +cindex(commands, complex) +A em(complex command) in zsh is one of the following: + +startitem() +findex(if) +cindex(if construct) +item(tt(if) var(list) tt(then) var(list) [ tt(elif) var(list) tt(then) var(list) ] ... [ tt(else) var(list) ] tt(fi))( +The tt(if) var(list) is executed, and if it returns a zero exit status, +the tt(then) var(list) is executed. +Otherwise, the tt(elif) var(list) is executed and if its value is zero, +the tt(then) var(list) is executed. +If each tt(elif) var(list) returns nonzero, the tt(else) var(list) is executed. +) +findex(for) +cindex(for loops) +cindex(loops, for) +item(tt(for) var(name) [ tt(in) var(word) ... var(term) ] tt(do) var(list) tt(done))( +where var(term) is at least one newline or tt(;). +Expand the list of var(word)s, and set the parameter +var(name) to each of them in turn, executing +var(list) each time. If the tt(in) var(word) is omitted, +use the positional parameters instead of the var(word)s. +) +item(tt(for LPAR()LPAR()) [var(expr1)] tt(;) [var(expr2)] tt(;) [var(expr3)] tt(RPAR()RPAR() do) var(list) tt(done))( +The arithmetic expression var(expr1) is evaluated first (see +noderef(Arithmetic Evaluation)). The arithmetic expression +var(expr2) is repeatedly evaluated until it evaluates to zero and +when non-zero, var(list) is executed and the arithmetic expression +var(expr3) evaluated. If any expression is omitted, then it behaves +as if it evaluated to 1. +) +findex(while) +cindex(while loops) +cindex(loops, while) +item(tt(while) var(list) tt(do) var(list) tt(done))( +Execute the tt(do) var(list) as long as the tt(while) var(list) +returns a zero exit status. +) +findex(until) +cindex(until loops) +cindex(loops, until) +item(tt(until) var(list) tt(do) var(list) tt(done))( +Execute the tt(do) var(list) as long as tt(until) var(list) +returns a nonzero exit status. +) +findex(repeat) +cindex(repeat loops) +cindex(loops, repeat) +item(tt(repeat) var(word) tt(do) var(list) tt(done))( +var(word) is expanded and treated as an arithmetic expression, +which must evaluate to a number var(n). +var(list) is then executed var(n) times. +) +findex(case) +cindex(case selection) +cindex(selection, case) +item(tt(case) var(word) tt(in) [ [tt(LPAR())] var(pattern) [ tt(|) var(pattern) ] ... tt(RPAR()) var(list) (tt(;;)|tt(;&)) ] ... tt(esac))( +Execute the var(list) associated with the first var(pattern) +that matches var(word), if any. The form of the patterns +is the same as that used for filename generation. See +noderef(Filename Generation). +If the var(list) that is executed is terminated with tt(;&) rather than +tt(;;), the following list is also executed. This continues until either +a list is terminated with tt(;;) or the tt(esac) is reached. +) +findex(select) +cindex(user selection) +cindex(selection, user) +item(tt(select) var(name) [ tt(in) var(word) ... var(term) ] tt(do) var(list) tt(done))( +where var(term) is one ore more newline or tt(;). +Print the set of var(word)s, each preceded by a number. +If the tt(in) var(word) is omitted, use the positional parameters. +The tt(PROMPT3) prompt is printed and a line is read from standard +input. If this line consists of the number of one of the listed +var(word)s, then the parameter var(name) +is set to the var(word) corresponding to this number. +If this line is empty, the selection list is printed again. +Otherwise, the value of the parameter var(name) is set to null. +The contents of the line read from standard input is saved +in the parameter tt(REPLY). var(list) is executed +for each selection until a break or end-of-file is encountered. +) +cindex(subshells) +item(tt(LPAR()) var(list) tt(RPAR()))( +Execute var(list) in a subshell. Traps set by the tt(trap) builtin +are reset to their default values while executing var(list). +) +item(tt({) var(list) tt(}))( +Execute var(list). +) +xitem(tt(function) var(word) ... [ tt(()) ] [ var(term) ] tt({) var(list) tt(})) +xitem(var(word) ... tt(()) [ var(term) ] tt({) var(list) tt(})) +item(var(word) ... tt(()) [ var(term) ] var(command))( +where var(term) is one or more newline or tt(;). +Define a function which is referenced by any one of var(word). +Normally, only one var(word) is provided; multiple var(word)s +are usually only useful for setting traps. +The body of the function is the var(list) between +the tt({) and tt(}). See noderef(Functions). +) +cindex(timing) +item(tt(time) [ var(pipeline) ])( +The var(pipeline) is executed, and timing statistics are +reported on the standard error in the form specified +by the tt(TIMEFMT) parameter. +If var(pipeline) is omitted, print statistics about the +shell process and its children. +) +cindex(testing conditional expression) +item(tt([[) var(exp) tt(]]))( +Evaluates the conditional expression var(exp) +and return a zero exit status if it is true. +See noderef(Conditional Expressions) +for a description of var(exp). +) +enditem() +texinode(Alternate Forms For Complex Commands)(Reserved Words)(Complex Commands)(Shell Grammar) +sect(Alternate Forms For Complex Commands) +cindex(alternate forms for complex commands) +cindex(commands, alternate forms for complex) +Many of zsh's complex commands have alternate forms. These particular +versions of complex commands should be considered deprecated and may be +removed in the future. The versions in the previous section should be +preferred instead. The short versions below only work if var(sublist) +is of the form `tt({) var(list) tt(})' or if the tt(SHORT_LOOPS) +option is set. + +startitem() +item(tt(if) var(list) tt({) var(list) tt(}) [ tt(elif) var(list) tt({) var(list) tt(}) ] ... [ tt(else {) var(list) tt(}) ])( +An alternate form of tt(if). +) +item(tt(if) var(list) var(sublist))( +A short form of the alternate `if'. +) +item(tt(for) var(name) tt(LPAR()) var(word) ... tt(RPAR()) var(sublist))( +A short form of tt(for). +) +item(tt(for) var(name) [ tt(in) var(word) ... var(term) ] var(sublist))( +where var(term) is at least one newline or tt(;). +Another short form of tt(for). +) +item(tt(for LPAR()LPAR()) [var(expr1)] tt(;) [var(expr2)] tt(;) [var(expr3)] tt(RPAR()RPAR()) var(sublist))( +A short form of the arithmetic tt(for) command. +) +item(tt(foreach) var(name) tt(LPAR()) var(word) ... tt(RPAR()) var(list) tt(end))( +Another form of tt(for). +) +item(tt(while) var(list) tt({) var(list) tt(}))( +An alternative form of tt(while). +) +item(tt(until) var(list) tt({) var(list) tt(}))( +An alternative form of tt(until). +) +item(tt(repeat) var(word) var(sublist))( +This is a short form of tt(repeat). +) +item(tt(case) var(word) tt({) [ [tt(LPAR())] var(pattern) [ tt(|) var(pattern) ] ... tt(RPAR()) var(list) (tt(;;)|tt(;&)) ] ... tt(}))( +An alternative form of tt(case). +) +item(tt(select) var(name) [ tt(in) var(word) var(term) ] var(sublist))( +where var(term) is at least one newline or tt(;). +A short form of tt(select). +) +enditem() +texinode(Reserved Words)(Comments)(Alternate Forms For Complex Commands)(Shell Grammar) +sect(Reserved Words) +cindex(reserved words) +findex(disable, use of) +The following words are recognized as reserved words when used as the first +word of a command unless quoted or disabled using tt(disable -r): + +tt(do done esac then elif else fi for case +if while function repeat time until +select coproc nocorrect foreach end ! [[ { }) + +Additionally, `tt(})' is recognized in any position if the tt(IGNORE_BRACES) option +is not set. +texinode(Comments)(Aliasing)(Reserved Words)(Shell Grammar) +sect(Comments) +cindex(comments) +pindex(INTERACTIVE_COMMENTS, use of) +vindex(histchars, use of) +In noninteractive shells, or in interactive shells with the +tt(INTERACTIVE_COMMENTS) option set, a word beginning +with the third character of the tt(histchars) parameter +(`tt(#)' by default) causes that word and all the following +characters up to a newline to be ignored. +texinode(Aliasing)(Quoting)(Comments)(Shell Grammar) +sect(Aliasing) +cindex(aliasing) +Every token in the shell input is checked to see if there +is an alias defined for it. +If so, it is replaced by the text of the alias if it is in command +position (if it could be the first word of a simple command), +or if the alias is global. +If the text ends with a space, the next word in the shell input +is treated as though it were in command position for purposes of alias +expansion. +findex(alias, use of) +cindex(aliases, global) +An alias is defined using the tt(alias) builtin; global aliases +may be defined using the tt(-g) option to that builtin. + +Alias substitution is done on the shell input before any +other substitution except history substitution. Therefore, +if an alias is defined for the word tt(foo), alias substitution +may be avoided by quoting part of the word, e.g. tt(\foo). +But there is nothing to prevent an alias being defined +for tt(\foo) as well. +texinode(Quoting)()(Aliasing)(Shell Grammar) +sect(Quoting) +cindex(quoting) +A character may be var(quoted) (that is, made +to stand for itself) by preceding it with a `tt(\)'. +`tt(\)' followed by a newline is ignored. + +A string enclosed between `tt($')' and `tt(')' is +processed the same way as the string arguments of the +tt(print) builtin, and the resulting string is considered to be +entirely quoted. A literal `tt(')' character can be included in the +string by using the `tt(\')' escape. + +All characters enclosed between a pair of single quotes (tt('')) that +is not preceded by a `tt($)' are quoted. A single quote cannot appear +within single quotes. + +Inside double quotes (tt("")), parameter and +command substitution occurs, and `tt(\)' quotes the characters +`tt(\)', `tt(`)', `tt(")', and `tt($)'. |