t4

unix v7是最后一个广泛发布的研究型UNIX版本

.bp
.SH
Appendix\ A\ -\ Grammar
.LP
.DS
\fIitem:		word
		input-output
		name = value
.sp 0.8
simple-command: item
		simple-command item
.sp 0.8
command:	simple-command
		\fB( \fIcommand-list \fB)
		\fB{ \fIcommand-list \fB}
		\fBfor \fIname \fBdo \fIcommand-list \fBdone
		\fBfor \fIname \fBin \fIword \*(ZZ \fBdo \fIcommand-list \fBdone
		\fBwhile \fIcommand-list \fBdo \fIcommand-list \fBdone
		\fBuntil \fIcommand-list \fBdo \fIcommand-list \fBdone
		\fBcase \fIword \fBin \fIcase-part \*(ZZ \fBesac
		\fBif \fIcommand-list \fBthen \fIcommand-list \fIelse-part \fBfi
.sp 0.8
\fIpipeline:		command
		pipeline \fB\*(VT\fI command
.sp 0.8
andor:		pipeline
		andor \fB&&\fI pipeline
		andor \fB\*(VT\*(VT\fI pipeline
.sp 0.8
command-list:	andor
		command-list \fB;\fI
		command-list \fB&\fI
		command-list \fB;\fI andor
		command-list \fB&\fI andor
.sp 0.8
input-output:	\fB> \fIfile
		\fB< \fIfile
		\fB\*(AP \fIword
		\fB\*(HE \fIword
.sp 0.8
file:		word
		\fB&\fI digit
		\fB&\fI \(mi
.sp 0.8
case-part:	pattern\fB ) \fIcommand-list\fB ;;
.sp 0.8
\fIpattern:		word
		pattern \fB\*(VT\fI word
.sp 0.8
\fIelse-part:	\fBelif \fIcommand-list\fB then\fI command-list else-part\fP
		\fBelse \fIcommand-list\fI
		empty
.sp 0.8
empty:
.sp 0.8
word:		\fRa sequence of non-blank characters\fI
.sp 0.8
name:		\fRa sequence of letters, digits or underscores starting with a letter\fI
.sp 0.8
digit:		\fB0 1 2 3 4 5 6 7 8 9\fP
.DE
.LP
.bp
.SH
Appendix\ B\ -\ Meta-characters\ and\ Reserved\ Words
.LP
a) syntactic
.RS
.IP \fB\*(VT\fR 6
pipe symbol
.IP \fB&&\fR 6
`andf' symbol
.IP \fB\*(VT\*(VT\fR 6
`orf' symbol
.IP \fB;\fP 6
command separator
.IP \fB;;\fP 6
case delimiter
.IP \fB&\fP 6
background commands
.IP \fB(\ )\fP 6
command grouping
.IP \fB<\fP 6
input redirection
.IP \fB\*(HE\fP 6
input from a here document
.IP \fB>\fP 6
output creation
.IP \fB\*(AP\fP 6
output append
.sp 2
.RE
.LP
b) patterns
.RS
.IP \fB\*(ST\fP 6
match any character(s) including none
.IP \fB?\fP 6
match any single character
.IP \fB[...]\fP 6
match any of the enclosed characters
.sp 2
.RE
.LP
c) substitution
.RS
.IP \fB${...}\fP 6
substitute shell variable
.IP \fB\`...\`\fP 6
substitute command output
.sp 2
.RE
.LP
d) quoting
.RS
.IP \fB\e\fP 6
quote the next character
.IP \fB\'...\'\fP 6
quote the enclosed characters except for \'
.IP \fB"\&..."\fR 6
quote the enclosed characters except
for \fB$ \` \e "\fP
.sp 2
.RE
.LP
e) reserved words
.DS
.ft B
if then else elif fi
case in esac
for while until do done
{  }
.ft
.DE