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.TH SH-SEXPRS 1
.SH NAME
sexprs, islist, els, text, textels, mktext, mklist, mktextlist \- parse and generate S-expressions
.SH SYNOPSIS
.B load sexprs
.B getsexprs
.I command
.br
.B islist
.I sexpr
.br
.B ${els
.IB sexpr }
.br
.B ${text
.IB sexpr }
.br
.B ${textels
.IB sexpr }
.br
.B ${mktext
.IB val }
.br
.B ${mklist
[
.IR val ...
.BR "" ] }
.br
.B ${mktextlist
[
.IR val ...
.BR "" ] }
.br
.SH DESCRIPTION
.B Sexprs
is a loadable module for
.IR sh (1)
that provides the facility to parse and generate
S-expressions (see
.IR sexprs (2)).
The following primitives are provided:
.TP 10
.B getsexprs
.B Getsexprs
works similiarly to
.B getlines
in
.IR sh-std (1).
It reads S-expressions from the standard input, and for expression read, it
invokes
.I command
with
.B $sexp
set to the text representation of that expression.
.B Getsexprs
recognises the usual loop
.B break
and
.B continue
exceptions.
.TP
.BI islist\ sexp
.B Islist
yields a nil (true) status if
.IR sexp ,
which must be a well-formed S-expression,
is a list element.
.TP
.BI ${els\ sexp }
If
.I sexp
is an S-expression containing a list,
then
.B els
returns a list of the S-expressions it contains.
It is an error if
.I sexp
is not a valid S-expression.
.TP
.BI ${text\ sexp }
If
.I sexp
is an S-expression containing a simple element,
then
.B text
returns the value of that element. If
.I sexp
is a list, the return value will be an empty string.
Note that elements
containing binary data will likely be corrupted
by conversion to utf-8.
It is an error if
.I sexp
is not a valid S-expression.
.TP
.BR ${textels\ sexp }
If
.I sexp
is an S-expression containing a list, then
.B textels
returns a list of the text values in that S-expression,
converted as with
.BR ${text} .
It is an error if
.I sexp
is not a valid S-expression.
.TP
.BR ${mktext\ val }
.B Mktext
returns a text representation of the S-expression
containing the simple value
.IR val .
.TP
.BR ${mklist\ \fR[\fPsexp\fR...]\fP }
.B Mklist
returns a text representation of the S-expression list
containing its arguments, which must be well-format
S-expressions.
.TP
.BR ${mktextlist\ \fR[\fPval\fR...]\fP }
.B Mktextlist
returns a text representation of the S-expression list
containing one simple element for each
.IR val .
.SH SOURCE
.B /appl/cmd/sh/sexprs.b
.SH SEE ALSO
.IR sh (1),
.IR sh-std (1),
.IR sexprs (2)
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