86 lines
2.5 KiB
Plaintext
86 lines
2.5 KiB
Plaintext
Gash Abstract Syntax Tree Specification
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***************************************
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Gash parses the shell language into an abstract syntax tree (AST) that
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has the following form.
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sync ::= exp
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| ('<sh-async> exp)
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exp ::= pipe
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| ('<sh-and> exp1 exp2)
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| ('<sh-or> exp1 exp2)
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| ('<sh-not> pipe)
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pipe ::= cmd*
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| ('<sh-pipeline> cmd* ...)
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cmd* ::= cmd
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| ('<sh-defun> name sync ...)
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cmd ::= ('<sh-exec> word ...)
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| ('<sh-exec-let> ((var var-word) ...) word ...)
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| ('<sh-with-redirects> (redir ...) [cmd])
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| ('<sh-set!> (var word) ...)
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| ('<sh-subshell> sync ...)
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| ('<sh-for> (name (word ...)) sync ...)
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| ('<sh-case> word ((pattern-word ...) sync ...) ...)
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| ('<sh-cond> (list sync ...) ... [('<sh-else> sync ...)])
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| ('<sh-while> list sync ...)
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| ('<sh-until> list sync ...)
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| ('<sh-begin> sync ...)
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redir ::= ('> fdes word)
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| ('< fdes word)
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| ('>& fdes word)
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| ('<& fdes word)
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| ('>> fdes word)
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| ('<> fdes word)
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| ('>! fdes word)
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| ('<< fdes word)
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Internally, the parser also uses these two forms:
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| ('<< fdes ('<sh-here-end> qword))
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| ('<<- fdes ('<sh-here-end> qword))
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word ::= string
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| (word ...)
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| ('<sh-quote> word)
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| ('<sh-cmd-sub> sync ...)
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| ('<sh-arithmetic> word)
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| ('<sh-ref> var)
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| ('<sh-ref-or> var [word])
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| ('<sh-ref-or*> var [word])
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| ('<sh-ref-or!> var [word])
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| ('<sh-ref-or!*> var [word])
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| ('<sh-ref-assert> var [word])
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| ('<sh-ref-assert*> var [word])
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| ('<sh-ref-and> var [word])
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| ('<sh-ref-and*> var [word])
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| ('<sh-ref-except-min> var [word])
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| ('<sh-ref-except-max> var [word])
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| ('<sh-ref-skip-min> var [word])
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| ('<sh-ref-skip-max> var [word])
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| ('<sh-ref-length> var)
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var ::= string
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| ("LINENO" integer)
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The parser never returns a qword, but it is a useful notion. It
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gets used internally by the parser and by the `word' module.
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qword ::= string
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| (qword ...)
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| ('<sh-quote> qword)
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Copying this file
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=================
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Copyright © 2018, 2019 Timothy Sample <samplet@ngyro.com>
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Copying and distribution of this file, with or without modification,
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are permitted in any medium without royalty provided the copyright
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notice and this notice are preserved. This file is offered as-is,
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without any warranty.
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