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Diffstat (limited to 'Doc/Zsh/params.yo')
| -rw-r--r-- | Doc/Zsh/params.yo | 105 |
1 files changed, 72 insertions, 33 deletions
diff --git a/Doc/Zsh/params.yo b/Doc/Zsh/params.yo index 3698829f3..dfda57281 100644 --- a/Doc/Zsh/params.yo +++ b/Doc/Zsh/params.yo @@ -1,48 +1,82 @@ texinode(Parameters)(Options)(Expansion)(Top) chapter(Parameters) cindex(parameters) +cindex(variables) sect(Description) A parameter has a name, a value, and a number of attributes. A name may be any sequence of alphanumeric characters and underscores, or the single characters `tt(*)', `tt(@)', `tt(#)', `tt(?)', `tt(-)', `tt($)', or `tt(!)'. -The value may be a em(scalar) (a string), -an integer, an array (indexed numerically), or an em(associative) -array (an unordered set of name-value pairs, indexed by name). To declare -the type of a parameter, or to assign a scalar or integer value to a -parameter, use the tt(typeset) builtin. +A parameter whose name begins with an alphanumeric or underscore is also +referred to as a em(variable). + +cindex(scalar) +cindex(parameters, scalar) +cindex(parameters, array) +cindex(parameters, associative array) +cindex(hash) +The attributes of a parameter determine the em(type) of its value, often +referred to as the parameter type or variable type, and also control +other processing that may be applied to the value when it is referenced. +The value type may be a em(scalar) (a string, an integer, or a floating +point number), an array (indexed numerically), or an em(associative) +array (an unordered set of name-value pairs, indexed by name, also +referred to as a em(hash)). + +cindex(export) +cindex(environment) +cindex(environment variables) +cindex(variables, environment) +Named scalar parameters may have the em(exported), tt(-x), attribute, to +copy them into the process environment, which is then passed from the +shell to any new processes that it starts. Exported parameters are called +em(environment variables). The shell also em(imports) environment variables +at startup time and automatically marks the corresponding parameters as +exported. Some environment variables are not imported for reasons of +security or because they would interfere with the correct operation of +other shell features. + +cindex(special parameters) +cindex(parameters, special) +Parameters may also be em(special), that is, they have a predetermined +meaning to the shell. Special parameters cannot have their type changed +or their readonly attribute turned off, and if a special parameter is +unset, then later recreated, the special properties will be retained. + +To declare the type of a parameter, or to assign a string or numeric value +to a scalar parameter, use the tt(typeset) builtin. findex(typeset, use of) The value of a scalar or integer parameter may also be assigned by writing: cindex(assignment) - +ifzman() indent(var(name)tt(=)var(value)) -If the integer attribute, tt(-i), is set for var(name), the var(value) -is subject to arithmetic evaluation. Furthermore, by replacing `tt(=)' -with `tt(+=)', a parameter can be added or appended to. - In scalar assignment, var(value) is expanded as a single string, in which the elements of arrays are joined together; filename expansion is -not performed unless the option tt(GLOB_ASSIGN) is set. See -noderef(Array Parameters) for additional forms of assignment. - -To refer to the value of a parameter, write `tt($)var(name)' or +not performed unless the option tt(GLOB_ASSIGN) is set. + +When the integer attribute, tt(-i), or a floating point attribute, tt(-E) +or tt(-F), is set for var(name), the var(value) is subject to arithmetic +evaluation. Furthermore, by replacing `tt(=)' with `tt(+=)', a parameter +can be incremented or appended to. See noderef(Array Parameters) and +ifzman(em(Arithmetic Evaluation) LPAR()in zmanref(zshexpn)RPAR())\ +ifnzman(noderef(Arithmetic Evaluation)) +for additional forms of assignment. + +Note that assignment may implicitly change the attributes of a parameter. +For example, assigning a number to a variable in arithmetic evaluation may +change its type to integer or float, and with tt(GLOB_ASSIGN) assigning a +pattern to a variable may change its type to an array. + +To reference the value of a parameter, write `tt($)var(name)' or `tt(${)var(name)tt(})'. See ifzman(em(Parameter Expansion) in zmanref(zshexpn))\ ifnzman(noderef(Parameter Expansion)) -for complete details. This section also explains the effect +for complete details. That section also explains the effect of the difference between scalar and array assignment on parameter expansion. - -In the parameter lists that follow, the mark `<S>' indicates that the -parameter is special. -Special parameters cannot have their type changed or their -readonly attribute turned off, and if a special parameter is unset, then -later recreated, the special properties will be retained. `<Z>' indicates -that the parameter does not exist when the shell initializes in tt(sh) or -tt(ksh) emulation mode. startmenu() menu(Array Parameters) menu(Positional Parameters) @@ -55,7 +89,7 @@ sect(Array Parameters) To assign an array value, write one of: findex(set, use of) cindex(array assignment) - +ifzman() indent(tt(set -A) var(name) var(value) ...) indent(var(name)tt(=LPAR())var(value) ...tt(RPAR())) @@ -63,16 +97,16 @@ If no parameter var(name) exists, an ordinary array parameter is created. If the parameter var(name) exists and is a scalar, it is replaced by a new array. Ordinary array parameters may also be explicitly declared with: findex(typeset, use of) - +ifzman() indent(tt(typeset -a) var(name)) Associative arrays em(must) be declared before assignment, by using: - +ifzman() indent(tt(typeset -A) var(name)) When var(name) refers to an associative array, the list in an assignment is interpreted as alternating keys and values: - +ifzman() indent(set -A var(name) var(key) var(value) ...) indent(var(name)tt(=LPAR())var(key) var(value) ...tt(RPAR())) @@ -81,13 +115,12 @@ assigns to the entire array, deleting any elements that do not appear in the list. To create an empty array (including associative arrays), use one of: - +ifzman() indent(tt(set -A) var(name)) indent(var(name)tt(=LPAR()RPAR())) subsect(Array Subscripts) cindex(subscripts) - Individual elements of an array may be selected using a subscript. A subscript of the form `tt([)var(exp)tt(])' selects the single element var(exp), where var(exp) is an arithmetic expression which will be subject @@ -150,7 +183,7 @@ For example, if tt(FOO) is set to `tt(foobar)', then subsect(Array Element Assignment) A subscript may be used on the left side of an assignment like so: - +ifzman() indent(var(name)tt([)var(exp)tt(]=)var(value)) In this form of assignment the element or range specified by var(exp) @@ -162,7 +195,7 @@ other elements to accommodate the new values. (This is not supported for associative arrays.) This syntax also works as an argument to the tt(typeset) command: - +ifzman() indent(tt(typeset) tt(")var(name)tt([)var(exp)tt(]"=)var(value)) The var(value) may em(not) be a parenthesized list in this case; only @@ -174,7 +207,7 @@ could be used instead. To delete an element of an ordinary array, assign `tt(LPAR()RPAR())' to that element. To delete an element of an associative array, use the tt(unset) command: - +ifzman() indent(tt(unset) tt(")var(name)tt([)var(exp)tt(]")) subsect(Subscript Flags) @@ -493,6 +526,10 @@ were never exported has been removed. texinode(Parameters Set By The Shell)(Parameters Used By The Shell)(Local Parameters)(Parameters) sect(Parameters Set By The Shell) +In the parameter lists that follow, the mark `<S>' indicates that the +parameter is special. `<Z>' indicates that the parameter does not exist +when the shell initializes in tt(sh) or tt(ksh) emulation mode. + The following parameters are automatically set by the shell: startitem() @@ -870,7 +907,9 @@ The version number of the release of zsh. enditem() texinode(Parameters Used By The Shell)()(Parameters Set By The Shell)(Parameters) sect(Parameters Used By The Shell) -The following parameters are used by the shell. +The following parameters are used by the shell. Again, `<S>' indicates +that the parameter is special and `<Z>' indicates that the parameter does +not exist when the shell initializes in tt(sh) or tt(ksh) emulation mode. In cases where there are two parameters with an upper- and lowercase form of the same name, such as tt(path) and tt(PATH), the lowercase form |