Why shell test with -o seems return a wrong result?
I am a newbie. I have read the man doc of test, and it say
EXPRESSION1 -o EXPRESSION2
either EXPRESSION1 or EXPRESSION2 is true
I run this in my shell:
[ false -o false ] && echo "what happened?"
and it print the string, why? :(
shell
asked Nov 12 at 1:51
Hawking Chyi
153
add a comment |
I am a newbie. I have read the man doc of test, and it say
EXPRESSION1 -o EXPRESSION2
either EXPRESSION1 or EXPRESSION2 is true
I run this in my shell:
[ false -o false ] && echo "what happened?"
and it print the string, why? :(
shell
asked Nov 12 at 1:51
Hawking Chyi
153
add a comment |
I am a newbie. I have read the man doc of test, and it say
EXPRESSION1 -o EXPRESSION2
either EXPRESSION1 or EXPRESSION2 is true
I run this in my shell:
[ false -o false ] && echo "what happened?"
and it print the string, why? :(
shell
asked Nov 12 at 1:51
Hawking Chyi
153
I am a newbie. I have read the man doc of test, and it say
EXPRESSION1 -o EXPRESSION2
either EXPRESSION1 or EXPRESSION2 is true
I run this in my shell:
[ false -o false ] && echo "what happened?"
and it print the string, why? :(
shell
shell
asked Nov 12 at 1:51
Hawking Chyi
153
asked Nov 12 at 1:51
Hawking Chyi
153
asked Nov 12 at 1:51
Hawking Chyi
153
asked Nov 12 at 1:51
Hawking Chyi
153
asked Nov 12 at 1:51
Hawking Chyi
153
153
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
From man test:
-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
The false is interpreted as a string. So [ false -o false ] is [ -n false -o -n false ]. As the string false has non-zero length (has 5 characters) the expression is true.
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
add a comment |
false in a test statement is just a string, and non-empty strings are truthy. Conversely:
$ false && false && echo 'Nope'
$ echo $?
1
answered Nov 12 at 1:58
l0b0
33.3k1583144
add a comment |
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2 Answers
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active
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2 Answers
2
active
oldest
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active
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active
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From man test:
-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
The false is interpreted as a string. So [ false -o false ] is [ -n false -o -n false ]. As the string false has non-zero length (has 5 characters) the expression is true.
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
add a comment |
From man test:
-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
The false is interpreted as a string. So [ false -o false ] is [ -n false -o -n false ]. As the string false has non-zero length (has 5 characters) the expression is true.
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
add a comment |
From man test:
-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
The false is interpreted as a string. So [ false -o false ] is [ -n false -o -n false ]. As the string false has non-zero length (has 5 characters) the expression is true.
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
From man test:
-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
The false is interpreted as a string. So [ false -o false ] is [ -n false -o -n false ]. As the string false has non-zero length (has 5 characters) the expression is true.
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
answered Nov 12 at 1:59
Kamil Cuk
8,6331523
8,6331523
add a comment |
add a comment |
false in a test statement is just a string, and non-empty strings are truthy. Conversely:
$ false && false && echo 'Nope'
$ echo $?
1
answered Nov 12 at 1:58
l0b0
33.3k1583144
add a comment |
false in a test statement is just a string, and non-empty strings are truthy. Conversely:
$ false && false && echo 'Nope'
$ echo $?
1
answered Nov 12 at 1:58
l0b0
33.3k1583144
add a comment |
false in a test statement is just a string, and non-empty strings are truthy. Conversely:
$ false && false && echo 'Nope'
$ echo $?
1
answered Nov 12 at 1:58
l0b0
33.3k1583144
false in a test statement is just a string, and non-empty strings are truthy. Conversely:
$ false && false && echo 'Nope'
$ echo $?
1
answered Nov 12 at 1:58
l0b0
33.3k1583144
answered Nov 12 at 1:58
l0b0
33.3k1583144
answered Nov 12 at 1:58
l0b0
33.3k1583144
answered Nov 12 at 1:58
l0b0
33.3k1583144
33.3k1583144
add a comment |
add a comment |
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