* Re: [9fans] inequality testing in shell
@ 2015-06-14 22:54 sl
2015-06-14 23:13 ` Neven Sajko
0 siblings, 1 reply; 7+ messages in thread
From: sl @ 2015-06-14 22:54 UTC (permalink / raw)
To: 9fans
TEST(1) TEST(1)
NAME
test - set status according to condition
SYNOPSIS
test expr
DESCRIPTION
Test evaluates the expression expr. If the value is true the
exit status is null; otherwise the exit status is non-null.
If there are no arguments the exit status is non-null.
The following primitives are used to construct expr.
-r file True if the file exists (is accessible) and is
readable.
-w file True if the file exists and is writable.
-x file True if the file exists and has execute permis-
sion.
-e file True if the file exists.
-f file True if the file exists and is a plain file.
-d file True if the file exists and is a directory.
-s file True if the file exists and has a size greater
than zero.
-t fildes True if the open file whose file descriptor num-
ber is fildes (1 by default) is the same file as
/dev/cons.
-A file True if the file exists and is append-only.
-L file True if the file exists and is exclusive-use.
-Tfile True if the file exists and is temporary.
s1 = s2 True if the strings s1 and s2 are identical.
s1 != s2 True if the strings s1 and s2 are not identical.
s1 True if s1 is not the null string. (Deprecated.)
-n s1 True if the length of string s1 is non-zero.
-z s1 True if the length of string s1 is zero.
n1 -eq n2 True if the integers n1 and n2 are arithmetically
equal. Any of the comparisons -ne, -gt, -ge,
-lt, or -le may be used in place of -eq. The
(nonstandard) construct -l string, meaning the
length of string, may be used in place of an
integer.
a -nt b True if file a is newer than (modified after)
file b.
a -ot b True if file a is older than (modified before)
file b.
f -older t True if file f is older than (modified before)
time t. If t is a integer followed by the letters
y(years), M(months), d(days), h(hours),
m(minutes), or s(seconds), it represents current
time minus the specified time. If there is no
letter, it represents seconds since epoch. You
can also concatenate mixed units. For example,
3d12h means three days and twelve hours ago.
These primaries may be combined with the following opera-
tors:
! unary negation operator
-o binary or operator
-a binary and operator; higher precedence than -o
( expr ) parentheses for grouping.
The primitives -b, -u, -g, and -s return false; they are
recognized for compatibility with POSIX.
Notice that all the operators and flags are separate argu-
ments to test. Notice also that parentheses and equal signs
are meaningful to rc and must be enclosed in quotes.
EXAMPLES
Test is a dubious way to check for specific character
strings: it uses a process to do what an rc(1) match or
switch statement can do. The first example is not only
inefficient but wrong, because test understands the pur-
ported string "-c" as an option.
if (test $1 '=' "-c") echo OK # wrong!
A better way is
if (~ $1 -c) echo OK
Test whether `abc' is in the current directory.
test -f abc -o -d abc
SOURCE
/sys/src/cmd/test.c
SEE ALSO
rc(1)
BUGS
Won't complain about extraneous arguments since there may be
arguments left unprocessed by short-circuit evaluation of -a
or -o.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] inequality testing in shell
2015-06-14 22:54 [9fans] inequality testing in shell sl
@ 2015-06-14 23:13 ` Neven Sajko
2015-06-14 23:30 ` Steve Simon
0 siblings, 1 reply; 7+ messages in thread
From: Neven Sajko @ 2015-06-14 23:13 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
> Any of the comparisons -ne, -gt, -ge, -lt, or -le may be used in place of -eq.
Oops :)
Sorry, I didn't notice that there under the -eq entry.
Thanks
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] inequality testing in shell
2015-06-14 23:13 ` Neven Sajko
@ 2015-06-14 23:30 ` Steve Simon
0 siblings, 0 replies; 7+ messages in thread
From: Steve Simon @ 2015-06-14 23:30 UTC (permalink / raw)
To: 9fans
> Oops :)
> Sorry, I didn't notice that there under the -eq entry.
ditto :-(
As I said, never used em.
-Steve
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] inequality testing in shell
2015-06-14 21:08 Neven Sajko
2015-06-14 21:28 ` Kurt H Maier
2015-06-14 22:11 ` Steve Simon
@ 2015-06-15 13:14 ` erik quanstrom
2 siblings, 0 replies; 7+ messages in thread
From: erik quanstrom @ 2015-06-15 13:14 UTC (permalink / raw)
To: 9fans
On Sun Jun 14 14:12:13 PDT 2015, nsajko@gmail.com wrote:
> Why doesn't the plan9 test program have features for checking
> inequalities (i.e. greater than etc.)?
> What do you guys do when you want to test for inequality?
>
> Maybe the most convenient way to do that in the shell would be if I
> made two tiny programs, lt & gt which would check their two arguments.
to be more pedantic than necessary, test is not part of the plan 9 shell.
the ~ operator is the way to test for (string) equality or inequality.
! is shell negation, so for non-negative integral x,
~ $x [1-3] -> x < 4
! ~ $x [1-3] -> x >= 4
the shell doesn't understand numbers.
outside the shell, hoc or awk are alternatives to test
- erik
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] inequality testing in shell
2015-06-14 21:08 Neven Sajko
2015-06-14 21:28 ` Kurt H Maier
@ 2015-06-14 22:11 ` Steve Simon
2015-06-15 13:14 ` erik quanstrom
2 siblings, 0 replies; 7+ messages in thread
From: Steve Simon @ 2015-06-14 22:11 UTC (permalink / raw)
To: 9fans
It would be easy to extend test to add these features,
you could submit a patch if you feel strongly.
To be honest I have never had the need for inequalaties,
perhaps I have been lucky.
-Steve
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [9fans] inequality testing in shell
2015-06-14 21:08 Neven Sajko
@ 2015-06-14 21:28 ` Kurt H Maier
2015-06-14 22:11 ` Steve Simon
2015-06-15 13:14 ` erik quanstrom
2 siblings, 0 replies; 7+ messages in thread
From: Kurt H Maier @ 2015-06-14 21:28 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
Quoting Neven Sajko <nsajko@gmail.com>:
> Why doesn't the plan9 test program have features for checking
> inequalities (i.e. greater than etc.)?
> What do you guys do when you want to test for inequality?
I use test(1) which does, in fact, support these features, as
described in the man page.
khm
^ permalink raw reply [flat|nested] 7+ messages in thread
* [9fans] inequality testing in shell
@ 2015-06-14 21:08 Neven Sajko
2015-06-14 21:28 ` Kurt H Maier
` (2 more replies)
0 siblings, 3 replies; 7+ messages in thread
From: Neven Sajko @ 2015-06-14 21:08 UTC (permalink / raw)
To: 9fans
Why doesn't the plan9 test program have features for checking
inequalities (i.e. greater than etc.)?
What do you guys do when you want to test for inequality?
Maybe the most convenient way to do that in the shell would be if I
made two tiny programs, lt & gt which would check their two arguments.
Regards,
Neven Sajko
^ permalink raw reply [flat|nested] 7+ messages in thread
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