[unix-history] / man / man1 / if.1

.th IF I 3/15/72
.sh NAME
if \*-  conditional command
.sh SYNOPSIS
.bd if
expr command [ arg ... ]
.sh DESCRIPTION
.it If
evaluates the expression
.it expr,
and if its value is
true,
executes the given
.it command
with the given arguments.
.s3
The following primitives are used to construct
the
.it expr:
.s3
.lp +10 10
\fB\*-r\fR|file	true if the file exists and is readable.
.s3
.lp +10 10
\fB\*-w|\fRfile	true if the file exists and is writable
.s3
.lp +10 10
s1|\fB=|\fRs2	true
if the strings
.it s1
and
.it s2
are equal.
.s3
.lp +10 10
s1|\fB!=|\fRs2	true
if the strings
.it s1
and
.it s2
are not equal.
.s3
.i0
These primaries may be combined with the
following operators:
.s3
.lp +10 10
\fB!\fR	unary negation operator
.s3
.lp +10 10
\fB\*-a\fR	binary
.it and
operator
.s3
.lp +10 10
\fB\*-o\fR	binary
.it or
operator
.s3
.lp +10 10
\fB(|\fRexpr\fB|)\fR	parentheses for grouping.
.s3
.i0
.bd \*-a
has higher precedence than
.bd \*-o.
Notice that all the operators and flags are separate
arguments to
.it if
and hence must be surrounded by spaces.
Notice also that parentheses are meaningful
to the Shell and must be escaped.
.sh "SEE ALSO"
sh(I)
.sh BUGS
Commit	Line	Data
41ec3b2b DR	1	.th IF I 3/15/72
	2	.sh NAME
	3	if \*- conditional command
	4	.sh SYNOPSIS
	5	.bd if
	6	expr command [ arg ... ]
	7	.sh DESCRIPTION
	8	.it If
	9	evaluates the expression
	10	.it expr,
	11	and if its value is
	12	true,
	13	executes the given
	14	.it command
	15	with the given arguments.
	16	.s3
	17	The following primitives are used to construct
	18	the
	19	.it expr:
	20	.s3
	21	.lp +10 10
	22	\fB\*-r\fR\|file true if the file exists and is readable.
	23	.s3
	24	.lp +10 10
	25	\fB\*-w\|\fRfile true if the file exists and is writable
	26	.s3
	27	.lp +10 10
	28	s1\|\fB=\|\fRs2 true
	29	if the strings
	30	.it s1
	31	and
	32	.it s2
	33	are equal.
	34	.s3
	35	.lp +10 10
	36	s1\|\fB!=\|\fRs2 true
	37	if the strings
	38	.it s1
	39	and
	40	.it s2
	41	are not equal.
	42	.s3
	43	.i0
	44	These primaries may be combined with the
	45	following operators:
	46	.s3
	47	.lp +10 10
	48	\fB!\fR unary negation operator
	49	.s3
	50	.lp +10 10
	51	\fB\*-a\fR binary
	52	.it and
	53	operator
	54	.s3
	55	.lp +10 10
	56	\fB\*-o\fR binary
	57	.it or
	58	operator
	59	.s3
	60	.lp +10 10
	61	\fB(\|\fRexpr\fB\|)\fR parentheses for grouping.
	62	.s3
	63	.i0
	64	.bd \*-a
65	has higher precedence than
66	.bd \*-o.
67	Notice that all the operators and flags are separate
68	arguments to
69	.it if
70	and hence must be surrounded by spaces.
71	Notice also that parentheses are meaningful
72	to the Shell and must be escaped.
73	.sh "SEE ALSO"
74	sh(I)
75	.sh BUGS