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How to determine if result of process substitution is a file path
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If I do this:
echo <(cat)
I get:
/dev/fd/63
so say at the command line I have:
myapp -f <(cat)
when I run it I get this error:
You need to pass a file after the -f flag. The resolved file path was:
'/dev/fd/63'. This path did not appear to exist on the filesystem.
How can I determine if the result of the process substitution is an actual file (for validation purposes)? Here is my bash code which generated the error:
if [[ -L "$file_path" ]]; then
file_path="$(readlink "$file_path")";
fi
if [[ ! -f "$file_path" ]]; then
echo "You need to pass a file after the -f flag. The resolved file path was: '$file_path'. This path did not appear to exist on the filesystem".;
return 1;
fi
if I get rid of my validation, code, I get this:
Could not open the following file for reading: /dev/fd/63 EBADF: bad
file descriptor, open '/dev/fd/63'
The node.js code I am using to read from the path is:
const fd = fs.openSync(file_path, 'r');
fs.read(fd, ...);
bash shell test read fd
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
|
show 2 more comments
If I do this:
echo <(cat)
I get:
/dev/fd/63
so say at the command line I have:
myapp -f <(cat)
when I run it I get this error:
You need to pass a file after the -f flag. The resolved file path was:
'/dev/fd/63'. This path did not appear to exist on the filesystem.
How can I determine if the result of the process substitution is an actual file (for validation purposes)? Here is my bash code which generated the error:
if [[ -L "$file_path" ]]; then
file_path="$(readlink "$file_path")";
fi
if [[ ! -f "$file_path" ]]; then
echo "You need to pass a file after the -f flag. The resolved file path was: '$file_path'. This path did not appear to exist on the filesystem".;
return 1;
fi
if I get rid of my validation, code, I get this:
Could not open the following file for reading: /dev/fd/63 EBADF: bad
file descriptor, open '/dev/fd/63'
The node.js code I am using to read from the path is:
const fd = fs.openSync(file_path, 'r');
fs.read(fd, ...);
bash shell test read fd
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
2
[ -f file ]tests iffileis a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a/dev/fd/n->/proc/self/fd/n"symlink" is some informative string liketype:[inum], not a path for pipes, sockets, etc.
– mosvy
8 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from/dev/fd/x, is there some way to do that?
– Alexander Mills
7 hours ago
1
maybe you should post a complete example;node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null)works for me.
– mosvy
7 hours ago
1
But simplycat <(cat)will not work from console, because thecatinside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.
– mosvy
7 hours ago
1
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,/dev/fd/Nare character special files (they aren't regular files, either). And on FreeBSD you should mountfdescfsif you want to access filedescs > 2 via/dev/fd/N.
– mosvy
7 hours ago
|
show 2 more comments
If I do this:
echo <(cat)
I get:
/dev/fd/63
so say at the command line I have:
myapp -f <(cat)
when I run it I get this error:
You need to pass a file after the -f flag. The resolved file path was:
'/dev/fd/63'. This path did not appear to exist on the filesystem.
How can I determine if the result of the process substitution is an actual file (for validation purposes)? Here is my bash code which generated the error:
if [[ -L "$file_path" ]]; then
file_path="$(readlink "$file_path")";
fi
if [[ ! -f "$file_path" ]]; then
echo "You need to pass a file after the -f flag. The resolved file path was: '$file_path'. This path did not appear to exist on the filesystem".;
return 1;
fi
if I get rid of my validation, code, I get this:
Could not open the following file for reading: /dev/fd/63 EBADF: bad
file descriptor, open '/dev/fd/63'
The node.js code I am using to read from the path is:
const fd = fs.openSync(file_path, 'r');
fs.read(fd, ...);
bash shell test read fd
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
If I do this:
echo <(cat)
I get:
/dev/fd/63
so say at the command line I have:
myapp -f <(cat)
when I run it I get this error:
You need to pass a file after the -f flag. The resolved file path was:
'/dev/fd/63'. This path did not appear to exist on the filesystem.
How can I determine if the result of the process substitution is an actual file (for validation purposes)? Here is my bash code which generated the error:
if [[ -L "$file_path" ]]; then
file_path="$(readlink "$file_path")";
fi
if [[ ! -f "$file_path" ]]; then
echo "You need to pass a file after the -f flag. The resolved file path was: '$file_path'. This path did not appear to exist on the filesystem".;
return 1;
fi
if I get rid of my validation, code, I get this:
Could not open the following file for reading: /dev/fd/63 EBADF: bad
file descriptor, open '/dev/fd/63'
The node.js code I am using to read from the path is:
const fd = fs.openSync(file_path, 'r');
fs.read(fd, ...);
bash shell test read fd
bash shell test read fd
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
edited 8 hours ago
Alexander Mills
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
asked 8 hours ago
Alexander MillsAlexander Mills
2,4642 gold badges21 silver badges67 bronze badges
2,4642 gold badges21 silver badges67 bronze badges
2
[ -f file ]tests iffileis a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a/dev/fd/n->/proc/self/fd/n"symlink" is some informative string liketype:[inum], not a path for pipes, sockets, etc.
– mosvy
8 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from/dev/fd/x, is there some way to do that?
– Alexander Mills
7 hours ago
1
maybe you should post a complete example;node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null)works for me.
– mosvy
7 hours ago
1
But simplycat <(cat)will not work from console, because thecatinside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.
– mosvy
7 hours ago
1
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,/dev/fd/Nare character special files (they aren't regular files, either). And on FreeBSD you should mountfdescfsif you want to access filedescs > 2 via/dev/fd/N.
– mosvy
7 hours ago
|
show 2 more comments
2
[ -f file ]tests iffileis a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a/dev/fd/n->/proc/self/fd/n"symlink" is some informative string liketype:[inum], not a path for pipes, sockets, etc.
– mosvy
8 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from/dev/fd/x, is there some way to do that?
– Alexander Mills
7 hours ago
1
maybe you should post a complete example;node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null)works for me.
– mosvy
7 hours ago
1
But simplycat <(cat)will not work from console, because thecatinside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.
– mosvy
7 hours ago
1
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,/dev/fd/Nare character special files (they aren't regular files, either). And on FreeBSD you should mountfdescfsif you want to access filedescs > 2 via/dev/fd/N.
– mosvy
7 hours ago
2
2
[ -f file ] tests if file is a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a /dev/fd/n -> /proc/self/fd/n "symlink" is some informative string like type:[inum], not a path for pipes, sockets, etc.– mosvy
8 hours ago
[ -f file ] tests if file is a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a /dev/fd/n -> /proc/self/fd/n "symlink" is some informative string like type:[inum], not a path for pipes, sockets, etc.– mosvy
8 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from
/dev/fd/x, is there some way to do that?– Alexander Mills
7 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from
/dev/fd/x, is there some way to do that?– Alexander Mills
7 hours ago
1
1
maybe you should post a complete example;
node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null) works for me.– mosvy
7 hours ago
maybe you should post a complete example;
node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null) works for me.– mosvy
7 hours ago
1
1
But simply
cat <(cat) will not work from console, because the cat inside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.– mosvy
7 hours ago
But simply
cat <(cat) will not work from console, because the cat inside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.– mosvy
7 hours ago
1
1
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,
/dev/fd/N are character special files (they aren't regular files, either). And on FreeBSD you should mount fdescfs if you want to access filedescs > 2 via /dev/fd/N.– mosvy
7 hours ago
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,
/dev/fd/N are character special files (they aren't regular files, either). And on FreeBSD you should mount fdescfs if you want to access filedescs > 2 via /dev/fd/N.– mosvy
7 hours ago
|
show 2 more comments
1 Answer
1
active
oldest
votes
To determine, in Bash, whether a string value is a path on your current system, use [[ -e "$path" ]]. This checks whether the path exists, and doesn't make any assumptions about the type of file it points to.
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
this definitely helps, thanks
– Alexander Mills
7 hours ago
add a comment |
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1 Answer
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1 Answer
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active
oldest
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active
oldest
votes
active
oldest
votes
To determine, in Bash, whether a string value is a path on your current system, use [[ -e "$path" ]]. This checks whether the path exists, and doesn't make any assumptions about the type of file it points to.
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
this definitely helps, thanks
– Alexander Mills
7 hours ago
add a comment |
To determine, in Bash, whether a string value is a path on your current system, use [[ -e "$path" ]]. This checks whether the path exists, and doesn't make any assumptions about the type of file it points to.
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
this definitely helps, thanks
– Alexander Mills
7 hours ago
add a comment |
To determine, in Bash, whether a string value is a path on your current system, use [[ -e "$path" ]]. This checks whether the path exists, and doesn't make any assumptions about the type of file it points to.
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
To determine, in Bash, whether a string value is a path on your current system, use [[ -e "$path" ]]. This checks whether the path exists, and doesn't make any assumptions about the type of file it points to.
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
answered 7 hours ago
l0b0l0b0
30.2k23 gold badges128 silver badges264 bronze badges
30.2k23 gold badges128 silver badges264 bronze badges
this definitely helps, thanks
– Alexander Mills
7 hours ago
add a comment |
this definitely helps, thanks
– Alexander Mills
7 hours ago
this definitely helps, thanks
– Alexander Mills
7 hours ago
this definitely helps, thanks
– Alexander Mills
7 hours ago
add a comment |
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2
[ -f file ]tests iffileis a regular file, and the file created by a process substitution is a pipe, not a regular file. Also, on Linux, the target of a/dev/fd/n->/proc/self/fd/n"symlink" is some informative string liketype:[inum], not a path for pipes, sockets, etc.– mosvy
8 hours ago
so much for everything is a file lulz..anyway I just want to be able to read from
/dev/fd/x, is there some way to do that?– Alexander Mills
7 hours ago
1
maybe you should post a complete example;
node -e 'fs=require("fs"); fs.openSync(process.argv[1], "r")' <(cat /dev/null)works for me.– mosvy
7 hours ago
1
But simply
cat <(cat)will not work from console, because thecatinside the process substitution may run in a different process group than the foreground one, and cannot read from the tty.– mosvy
7 hours ago
1
I don't have a MacOS system. But someone else may have, so post a complete reproducible testcase. FWIW, on BSD,
/dev/fd/Nare character special files (they aren't regular files, either). And on FreeBSD you should mountfdescfsif you want to access filedescs > 2 via/dev/fd/N.– mosvy
7 hours ago