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In a symlink pointing to '127.0.1.1:+xxxxx', what is the plus character for?
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On my Linux filesystem, a symlinks points to 127.0.1.1:+xxxxx.
Why the plus sign? Could there also be a minus? Why not just 127.0.1.1:xxxxx?
linux networking symbolic-link ip-address
edited 18 mins ago
muru
699419
asked 9 hours ago
myMethod
684
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myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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up vote
13
down vote
favorite
On my Linux filesystem, a symlinks points to 127.0.1.1:+xxxxx.
Why the plus sign? Could there also be a minus? Why not just 127.0.1.1:xxxxx?
linux networking symbolic-link ip-address
edited 18 mins ago
muru
699419
asked 9 hours ago
myMethod
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Is this symbolic link under /proc?
– Joshua
5 hours ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago
add a comment |Â
up vote
13
down vote
favorite
up vote
13
down vote
favorite
On my Linux filesystem, a symlinks points to 127.0.1.1:+xxxxx.
Why the plus sign? Could there also be a minus? Why not just 127.0.1.1:xxxxx?
linux networking symbolic-link ip-address
edited 18 mins ago
muru
699419
asked 9 hours ago
myMethod
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
On my Linux filesystem, a symlinks points to 127.0.1.1:+xxxxx.
Why the plus sign? Could there also be a minus? Why not just 127.0.1.1:xxxxx?
linux networking symbolic-link ip-address
linux networking symbolic-link ip-address
edited 18 mins ago
muru
699419
asked 9 hours ago
myMethod
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 18 mins ago
muru
699419
asked 9 hours ago
myMethod
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 18 mins ago
muru
699419
edited 18 mins ago
muru
699419
edited 18 mins ago
muru
699419
699419
asked 9 hours ago
myMethod
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 9 hours ago
myMethod
684
asked 9 hours ago
myMethod
684
684
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
myMethod is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Is this symbolic link under /proc?
– Joshua
5 hours ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago
add a comment |Â
Is this symbolic link under /proc?
– Joshua
5 hours ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago
Is this symbolic link under /proc?
– Joshua
5 hours ago
Is this symbolic link under /proc?
– Joshua
5 hours ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
17
down vote
accepted
Symbolic links which don't point to a file have no generic meaning at all. In this case it might be the process ID, or a port with some special protocol spoken over it, or another identifier. It all depends on what program made it.
Software which creates these links simply takes advantage of the facts that 1) a symlink's target may be non-existent or even total nonsense; 2) creating a symlink is a single-syscall completely atomic operation (as is reading its target), unlike creating a regular file which takes at least 3 separate system calls.
Thus symlink creation can be abused as a way of locking (ensuring single instance of a program) even when other mechanisms may be unreliable. The program doesn't need the symlink to actually resolve to a real file: it only cares about whether creating the link succeeds, or whether it fails due to it already existing.
answered 8 hours ago
grawity
220k32449514
1
Thank you for the detailed answer.
– myMethod
8 hours ago
add a comment |Â
up vote
9
down vote
As far as I know the "+" means that the number after the IP (the "xxxxx") refers to a "process ID" (not a port which usually uses the notation [IP-address]:[portnumber]).
answered 8 hours ago
Albin
1,250621
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like/procor/dev. Can you explain what this symlink is used for?
– Barmar
2 hours ago
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
17
down vote
accepted
Symbolic links which don't point to a file have no generic meaning at all. In this case it might be the process ID, or a port with some special protocol spoken over it, or another identifier. It all depends on what program made it.
Software which creates these links simply takes advantage of the facts that 1) a symlink's target may be non-existent or even total nonsense; 2) creating a symlink is a single-syscall completely atomic operation (as is reading its target), unlike creating a regular file which takes at least 3 separate system calls.
Thus symlink creation can be abused as a way of locking (ensuring single instance of a program) even when other mechanisms may be unreliable. The program doesn't need the symlink to actually resolve to a real file: it only cares about whether creating the link succeeds, or whether it fails due to it already existing.
answered 8 hours ago
grawity
220k32449514
1
Thank you for the detailed answer.
– myMethod
8 hours ago
add a comment |Â
up vote
17
down vote
accepted
Symbolic links which don't point to a file have no generic meaning at all. In this case it might be the process ID, or a port with some special protocol spoken over it, or another identifier. It all depends on what program made it.
Software which creates these links simply takes advantage of the facts that 1) a symlink's target may be non-existent or even total nonsense; 2) creating a symlink is a single-syscall completely atomic operation (as is reading its target), unlike creating a regular file which takes at least 3 separate system calls.
Thus symlink creation can be abused as a way of locking (ensuring single instance of a program) even when other mechanisms may be unreliable. The program doesn't need the symlink to actually resolve to a real file: it only cares about whether creating the link succeeds, or whether it fails due to it already existing.
answered 8 hours ago
grawity
220k32449514
1
Thank you for the detailed answer.
– myMethod
8 hours ago
add a comment |Â
up vote
17
down vote
accepted
up vote
17
down vote
accepted
Symbolic links which don't point to a file have no generic meaning at all. In this case it might be the process ID, or a port with some special protocol spoken over it, or another identifier. It all depends on what program made it.
Software which creates these links simply takes advantage of the facts that 1) a symlink's target may be non-existent or even total nonsense; 2) creating a symlink is a single-syscall completely atomic operation (as is reading its target), unlike creating a regular file which takes at least 3 separate system calls.
Thus symlink creation can be abused as a way of locking (ensuring single instance of a program) even when other mechanisms may be unreliable. The program doesn't need the symlink to actually resolve to a real file: it only cares about whether creating the link succeeds, or whether it fails due to it already existing.
answered 8 hours ago
grawity
220k32449514
Symbolic links which don't point to a file have no generic meaning at all. In this case it might be the process ID, or a port with some special protocol spoken over it, or another identifier. It all depends on what program made it.
Software which creates these links simply takes advantage of the facts that 1) a symlink's target may be non-existent or even total nonsense; 2) creating a symlink is a single-syscall completely atomic operation (as is reading its target), unlike creating a regular file which takes at least 3 separate system calls.
Thus symlink creation can be abused as a way of locking (ensuring single instance of a program) even when other mechanisms may be unreliable. The program doesn't need the symlink to actually resolve to a real file: it only cares about whether creating the link succeeds, or whether it fails due to it already existing.
answered 8 hours ago
grawity
220k32449514
answered 8 hours ago
grawity
220k32449514
answered 8 hours ago
grawity
220k32449514
answered 8 hours ago
grawity
220k32449514
220k32449514
1
Thank you for the detailed answer.
– myMethod
8 hours ago
add a comment |Â
1
Thank you for the detailed answer.
– myMethod
8 hours ago
1
1
Thank you for the detailed answer.
– myMethod
8 hours ago
Thank you for the detailed answer.
– myMethod
8 hours ago
add a comment |Â
up vote
9
down vote
As far as I know the "+" means that the number after the IP (the "xxxxx") refers to a "process ID" (not a port which usually uses the notation [IP-address]:[portnumber]).
answered 8 hours ago
Albin
1,250621
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like/procor/dev. Can you explain what this symlink is used for?
– Barmar
2 hours ago
add a comment |Â
up vote
9
down vote
As far as I know the "+" means that the number after the IP (the "xxxxx") refers to a "process ID" (not a port which usually uses the notation [IP-address]:[portnumber]).
answered 8 hours ago
Albin
1,250621
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like/procor/dev. Can you explain what this symlink is used for?
– Barmar
2 hours ago
add a comment |Â
up vote
9
down vote
up vote
9
down vote
As far as I know the "+" means that the number after the IP (the "xxxxx") refers to a "process ID" (not a port which usually uses the notation [IP-address]:[portnumber]).
answered 8 hours ago
Albin
1,250621
As far as I know the "+" means that the number after the IP (the "xxxxx") refers to a "process ID" (not a port which usually uses the notation [IP-address]:[portnumber]).
answered 8 hours ago
Albin
1,250621
answered 8 hours ago
Albin
1,250621
answered 8 hours ago
Albin
1,250621
answered 8 hours ago
Albin
1,250621
1,250621
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like/procor/dev. Can you explain what this symlink is used for?
– Barmar
2 hours ago
add a comment |Â
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like/procor/dev. Can you explain what this symlink is used for?
– Barmar
2 hours ago
I just checked it. In my case it really does.
– myMethod
8 hours ago
I just checked it. In my case it really does.
– myMethod
8 hours ago
1
1
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
@myMethod glad to help, feel free to "accept" my answer, if it answered you're question.
– Albin
8 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Is there documentation of this format somewhere that you could link to?
– David Z
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
Not sure, I just remember it from hands on experience.
– Albin
7 hours ago
It sounds like you're talking about a symlink in a special directory, like
/proc or /dev. Can you explain what this symlink is used for?– Barmar
2 hours ago
It sounds like you're talking about a symlink in a special directory, like
/proc or /dev. Can you explain what this symlink is used for?– Barmar
2 hours ago
add a comment |Â
myMethod is a new contributor. Be nice, and check out our Code of Conduct.
myMethod is a new contributor. Be nice, and check out our Code of Conduct.
myMethod is a new contributor. Be nice, and check out our Code of Conduct.
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Is this symbolic link under /proc?
– Joshua
5 hours ago
@Joshua: More likely under ~/.mozilla/ or similar. Firefox/Thunderbird, and iirc Steam, use such symlinks for locking.
– grawity
4 mins ago