What's Linux test -a command test for?
Please take a look at the following code,
snap=snapshot.file
touch snapshot.file-1
$ [ -a $snap-1 ] && echo yes
yes
What does the test -a command tests for here?
I tried info coreutils 'test invocation' and searched for -a, but didn't find it in the file characteristic tests section, but rather in the connectives for test section.
Is such test -a command an undocumented one?
NB, My system is Ubuntu 13.10 and my man test says GNU coreutils 8.20 October 2012 TEST(1).
linux ubuntu command-line command-line-arguments
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
add a comment |
Please take a look at the following code,
snap=snapshot.file
touch snapshot.file-1
$ [ -a $snap-1 ] && echo yes
yes
What does the test -a command tests for here?
I tried info coreutils 'test invocation' and searched for -a, but didn't find it in the file characteristic tests section, but rather in the connectives for test section.
Is such test -a command an undocumented one?
NB, My system is Ubuntu 13.10 and my man test says GNU coreutils 8.20 October 2012 TEST(1).
linux ubuntu command-line command-line-arguments
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
add a comment |
Please take a look at the following code,
snap=snapshot.file
touch snapshot.file-1
$ [ -a $snap-1 ] && echo yes
yes
What does the test -a command tests for here?
I tried info coreutils 'test invocation' and searched for -a, but didn't find it in the file characteristic tests section, but rather in the connectives for test section.
Is such test -a command an undocumented one?
NB, My system is Ubuntu 13.10 and my man test says GNU coreutils 8.20 October 2012 TEST(1).
linux ubuntu command-line command-line-arguments
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
Please take a look at the following code,
snap=snapshot.file
touch snapshot.file-1
$ [ -a $snap-1 ] && echo yes
yes
What does the test -a command tests for here?
I tried info coreutils 'test invocation' and searched for -a, but didn't find it in the file characteristic tests section, but rather in the connectives for test section.
Is such test -a command an undocumented one?
NB, My system is Ubuntu 13.10 and my man test says GNU coreutils 8.20 October 2012 TEST(1).
linux ubuntu command-line command-line-arguments
linux ubuntu command-line command-line-arguments
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
edited Feb 21 at 16:53
xpt
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
asked Jun 17 '14 at 1:33
xptxpt
3,216145693
3,216145693
add a comment |
add a comment |
3 Answers
3
active
oldest
votes
I am not sure why the info page doesn't have it, but running help test in bash gives the answer:
...
File operators:
-a FILE True if file exists.
...
So it is simply an "existence" test, no other permissions/attributes checked.
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
Perfect! Thanks. Strange,man testdoesn't have that either. onlyhelp testdoes. Does that mean it is abashspecific file existence testing?
– xpt
Jun 17 '14 at 3:57
1
@xpt It would seem like that is the case, but for me/bin/test -a fileworked also...So why it isn't in the manpage I have NO idea.
– BenjiWiebe
Jun 17 '14 at 12:13
add a comment |
If you're running test or [ in bash, it's actually probably the built-in version, and not the coreutils version in /usr/bin:
$ type test
test is a shell builtin
$ type [
[ is a shell builtin
That said, it does appear that the coreutils version implements both -a and -e, with exactly the same behavior. Maybe -a is not reflected in the manpage because it's not standard, so maybe it was added later and that person neglected to update the manpage accordingly. But I can't say I know the history behind why it was added (or even what the a is supposed to be short for).
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
add a comment |
-a is the AND operator for combining conditions, so the following shows yes if both directories exist:
[ -e /root -a -e /usr ] && echo yes
The use of it with a single condition that defaults to an existance test seems like retained old behavior but I can't find it in old man pages.
Reference (scroll down some after info coreutils 'test invocation'):
16.3.6 Connectives for `test'
The usual logical connectives.
`! EXPR'
True if EXPR is false.
`EXPR1 -a EXPR2'
True if both EXPR1 and EXPR2 are true.
`EXPR1 -o EXPR2'
True if either EXPR1 or EXPR2 is true.
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
1
If you look at the coreutils source, theaandecases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.
– jjlin
Jun 17 '14 at 17:33
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
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votes
active
oldest
votes
I am not sure why the info page doesn't have it, but running help test in bash gives the answer:
...
File operators:
-a FILE True if file exists.
...
So it is simply an "existence" test, no other permissions/attributes checked.
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
Perfect! Thanks. Strange,man testdoesn't have that either. onlyhelp testdoes. Does that mean it is abashspecific file existence testing?
– xpt
Jun 17 '14 at 3:57
1
@xpt It would seem like that is the case, but for me/bin/test -a fileworked also...So why it isn't in the manpage I have NO idea.
– BenjiWiebe
Jun 17 '14 at 12:13
add a comment |
I am not sure why the info page doesn't have it, but running help test in bash gives the answer:
...
File operators:
-a FILE True if file exists.
...
So it is simply an "existence" test, no other permissions/attributes checked.
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
Perfect! Thanks. Strange,man testdoesn't have that either. onlyhelp testdoes. Does that mean it is abashspecific file existence testing?
– xpt
Jun 17 '14 at 3:57
1
@xpt It would seem like that is the case, but for me/bin/test -a fileworked also...So why it isn't in the manpage I have NO idea.
– BenjiWiebe
Jun 17 '14 at 12:13
add a comment |
I am not sure why the info page doesn't have it, but running help test in bash gives the answer:
...
File operators:
-a FILE True if file exists.
...
So it is simply an "existence" test, no other permissions/attributes checked.
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
I am not sure why the info page doesn't have it, but running help test in bash gives the answer:
...
File operators:
-a FILE True if file exists.
...
So it is simply an "existence" test, no other permissions/attributes checked.
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
answered Jun 17 '14 at 1:42
BenjiWiebeBenjiWiebe
6,74093558
6,74093558
Perfect! Thanks. Strange,man testdoesn't have that either. onlyhelp testdoes. Does that mean it is abashspecific file existence testing?
– xpt
Jun 17 '14 at 3:57
1
@xpt It would seem like that is the case, but for me/bin/test -a fileworked also...So why it isn't in the manpage I have NO idea.
– BenjiWiebe
Jun 17 '14 at 12:13
add a comment |
Perfect! Thanks. Strange,man testdoesn't have that either. onlyhelp testdoes. Does that mean it is abashspecific file existence testing?
– xpt
Jun 17 '14 at 3:57
1
@xpt It would seem like that is the case, but for me/bin/test -a fileworked also...So why it isn't in the manpage I have NO idea.
– BenjiWiebe
Jun 17 '14 at 12:13
Perfect! Thanks. Strange,
man test doesn't have that either. only help test does. Does that mean it is a bash specific file existence testing?– xpt
Jun 17 '14 at 3:57
Perfect! Thanks. Strange,
man test doesn't have that either. only help test does. Does that mean it is a bash specific file existence testing?– xpt
Jun 17 '14 at 3:57
1
1
@xpt It would seem like that is the case, but for me
/bin/test -a file worked also...So why it isn't in the manpage I have NO idea.– BenjiWiebe
Jun 17 '14 at 12:13
@xpt It would seem like that is the case, but for me
/bin/test -a file worked also...So why it isn't in the manpage I have NO idea.– BenjiWiebe
Jun 17 '14 at 12:13
add a comment |
If you're running test or [ in bash, it's actually probably the built-in version, and not the coreutils version in /usr/bin:
$ type test
test is a shell builtin
$ type [
[ is a shell builtin
That said, it does appear that the coreutils version implements both -a and -e, with exactly the same behavior. Maybe -a is not reflected in the manpage because it's not standard, so maybe it was added later and that person neglected to update the manpage accordingly. But I can't say I know the history behind why it was added (or even what the a is supposed to be short for).
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
add a comment |
If you're running test or [ in bash, it's actually probably the built-in version, and not the coreutils version in /usr/bin:
$ type test
test is a shell builtin
$ type [
[ is a shell builtin
That said, it does appear that the coreutils version implements both -a and -e, with exactly the same behavior. Maybe -a is not reflected in the manpage because it's not standard, so maybe it was added later and that person neglected to update the manpage accordingly. But I can't say I know the history behind why it was added (or even what the a is supposed to be short for).
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
add a comment |
If you're running test or [ in bash, it's actually probably the built-in version, and not the coreutils version in /usr/bin:
$ type test
test is a shell builtin
$ type [
[ is a shell builtin
That said, it does appear that the coreutils version implements both -a and -e, with exactly the same behavior. Maybe -a is not reflected in the manpage because it's not standard, so maybe it was added later and that person neglected to update the manpage accordingly. But I can't say I know the history behind why it was added (or even what the a is supposed to be short for).
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
If you're running test or [ in bash, it's actually probably the built-in version, and not the coreutils version in /usr/bin:
$ type test
test is a shell builtin
$ type [
[ is a shell builtin
That said, it does appear that the coreutils version implements both -a and -e, with exactly the same behavior. Maybe -a is not reflected in the manpage because it's not standard, so maybe it was added later and that person neglected to update the manpage accordingly. But I can't say I know the history behind why it was added (or even what the a is supposed to be short for).
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
answered Jun 17 '14 at 5:17
jjlinjjlin
11.9k33842
11.9k33842
add a comment |
add a comment |
-a is the AND operator for combining conditions, so the following shows yes if both directories exist:
[ -e /root -a -e /usr ] && echo yes
The use of it with a single condition that defaults to an existance test seems like retained old behavior but I can't find it in old man pages.
Reference (scroll down some after info coreutils 'test invocation'):
16.3.6 Connectives for `test'
The usual logical connectives.
`! EXPR'
True if EXPR is false.
`EXPR1 -a EXPR2'
True if both EXPR1 and EXPR2 are true.
`EXPR1 -o EXPR2'
True if either EXPR1 or EXPR2 is true.
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
1
If you look at the coreutils source, theaandecases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.
– jjlin
Jun 17 '14 at 17:33
add a comment |
-a is the AND operator for combining conditions, so the following shows yes if both directories exist:
[ -e /root -a -e /usr ] && echo yes
The use of it with a single condition that defaults to an existance test seems like retained old behavior but I can't find it in old man pages.
Reference (scroll down some after info coreutils 'test invocation'):
16.3.6 Connectives for `test'
The usual logical connectives.
`! EXPR'
True if EXPR is false.
`EXPR1 -a EXPR2'
True if both EXPR1 and EXPR2 are true.
`EXPR1 -o EXPR2'
True if either EXPR1 or EXPR2 is true.
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
1
If you look at the coreutils source, theaandecases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.
– jjlin
Jun 17 '14 at 17:33
add a comment |
-a is the AND operator for combining conditions, so the following shows yes if both directories exist:
[ -e /root -a -e /usr ] && echo yes
The use of it with a single condition that defaults to an existance test seems like retained old behavior but I can't find it in old man pages.
Reference (scroll down some after info coreutils 'test invocation'):
16.3.6 Connectives for `test'
The usual logical connectives.
`! EXPR'
True if EXPR is false.
`EXPR1 -a EXPR2'
True if both EXPR1 and EXPR2 are true.
`EXPR1 -o EXPR2'
True if either EXPR1 or EXPR2 is true.
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
-a is the AND operator for combining conditions, so the following shows yes if both directories exist:
[ -e /root -a -e /usr ] && echo yes
The use of it with a single condition that defaults to an existance test seems like retained old behavior but I can't find it in old man pages.
Reference (scroll down some after info coreutils 'test invocation'):
16.3.6 Connectives for `test'
The usual logical connectives.
`! EXPR'
True if EXPR is false.
`EXPR1 -a EXPR2'
True if both EXPR1 and EXPR2 are true.
`EXPR1 -o EXPR2'
True if either EXPR1 or EXPR2 is true.
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
edited Dec 24 '17 at 14:56
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
answered Jun 17 '14 at 13:46
BrianBrian
8,2511833
8,2511833
1
If you look at the coreutils source, theaandecases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.
– jjlin
Jun 17 '14 at 17:33
add a comment |
1
If you look at the coreutils source, theaandecases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.
– jjlin
Jun 17 '14 at 17:33
1
1
If you look at the coreutils source, the
a and e cases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.– jjlin
Jun 17 '14 at 17:33
If you look at the coreutils source, the
a and e cases share the same code in the function that handles unary operators, so I don't think it's an accidental thing.– jjlin
Jun 17 '14 at 17:33
add a comment |
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