Temporary folder that automatically destroyed after process exit

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3
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Can we use temporary folders like temporary files

TMP=$(mktemp ... )
exec 3<>$TMP
rm $TMP

cat <&3

which will be destroyed automatically after this shell exit?

asked 2 hours ago

Bob Johnson

241

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up vote
3
down vote

favorite

Can we use temporary folders like temporary files

TMP=$(mktemp ... )
exec 3<>$TMP
rm $TMP

cat <&3

which will be destroyed automatically after this shell exit?

asked 2 hours ago

Bob Johnson

241

New contributor

add a commentÂ |Â

up vote
3
down vote

favorite

Can we use temporary folders like temporary files

TMP=$(mktemp ... )
exec 3<>$TMP
rm $TMP

cat <&3

which will be destroyed automatically after this shell exit?

asked 2 hours ago

Bob Johnson

241

New contributor

Can we use temporary folders like temporary files

TMP=$(mktemp ... )
exec 3<>$TMP
rm $TMP

cat <&3

which will be destroyed automatically after this shell exit?

file-descriptors tmpfs

asked 2 hours ago

Bob Johnson

241

New contributor

asked 2 hours ago

Bob Johnson

241

New contributor

asked 2 hours ago

Bob Johnson

241

New contributor

asked 2 hours ago

Bob Johnson

241

asked 2 hours ago

Bob Johnson

241

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3 Answers
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3
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In the case of a temporary file, your example in the question would create it, then unlink it from the directory (making it "disappear"), and when the script closes the filedescriptor (probably upon termination), the space taken by the file would be reclaimable by the system. This is a common way to deal with temporary files in languages like C.

It is, as far as I know, not possible to open a directory in the same way in the shell. The code examples given below avoids having to juggle filedescriptors completely.

A common way to delete temporary files and directories at the termination of a script is by installing a cleanup EXIT trap:

tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap 'rm -f "$tmpfile"; rm -rf "$tmpdir"' EXIT

# The rest of the script goes here.

Or you may call a cleanup function:

cleanup () 
 rm -f "$tmpfile"
 rm -rf "$tmpdir"


tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap cleanup EXIT

# The rest of the script goes here.

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

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up vote
1
down vote

Write a shell-function that will be executed when your script if finished. In the example below I call it 'cleanup' and set a trap to be executed on exit levels 1 2 3 6

trap cleanup 0 1 2 3 6

cleanup()

 [ -d $TMP ] && rm -rf $TMP

See this post for more info.

answered 2 hours ago

Dirk Krijgsman

4546

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up vote
1
down vote

You can chdir into it and then remove it, provided that you don't try to use paths inside it afterwards:

#! /bin/sh
dir=`mktemp -d`
cd "$dir"
exec 4>file 3<file
rm -fr "$dir"

echo yes >&4 # OK
cat <&3 # OK

cat file # FAIL
echo yes > file # FAIL

I haven't checked, but it's most probably the same problem when using openat(2) in C with a directory that no longer exists in the file system.

If you're root, you can play with a separate namespace, and mount -t tmpfs tmpfs /dir inside it.

The cannonical answers (set a trap on EXIT) don't work if your script is forced into an unclean exit (eg. with SIGKILL); that may leave sensitive data hanging around.

edited 17 mins ago

answered 59 mins ago

qubert

3955

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3 Answers
3

active

oldest

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3 Answers
3

active

oldest

votes

up vote
3
down vote

It is, as far as I know, not possible to open a directory in the same way in the shell. The code examples given below avoids having to juggle filedescriptors completely.

A common way to delete temporary files and directories at the termination of a script is by installing a cleanup EXIT trap:

tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap 'rm -f "$tmpfile"; rm -rf "$tmpdir"' EXIT

# The rest of the script goes here.

Or you may call a cleanup function:

cleanup () 
 rm -f "$tmpfile"
 rm -rf "$tmpdir"


tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap cleanup EXIT

# The rest of the script goes here.

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

add a commentÂ |Â

up vote
3
down vote

It is, as far as I know, not possible to open a directory in the same way in the shell. The code examples given below avoids having to juggle filedescriptors completely.

A common way to delete temporary files and directories at the termination of a script is by installing a cleanup EXIT trap:

tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap 'rm -f "$tmpfile"; rm -rf "$tmpdir"' EXIT

# The rest of the script goes here.

Or you may call a cleanup function:

cleanup () 
 rm -f "$tmpfile"
 rm -rf "$tmpdir"


tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap cleanup EXIT

# The rest of the script goes here.

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

add a commentÂ |Â

up vote
3
down vote

It is, as far as I know, not possible to open a directory in the same way in the shell. The code examples given below avoids having to juggle filedescriptors completely.

A common way to delete temporary files and directories at the termination of a script is by installing a cleanup EXIT trap:

tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap 'rm -f "$tmpfile"; rm -rf "$tmpdir"' EXIT

# The rest of the script goes here.

Or you may call a cleanup function:

cleanup () 
 rm -f "$tmpfile"
 rm -rf "$tmpdir"


tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap cleanup EXIT

# The rest of the script goes here.

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

It is, as far as I know, not possible to open a directory in the same way in the shell. The code examples given below avoids having to juggle filedescriptors completely.

A common way to delete temporary files and directories at the termination of a script is by installing a cleanup EXIT trap:

tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap 'rm -f "$tmpfile"; rm -rf "$tmpdir"' EXIT

# The rest of the script goes here.

Or you may call a cleanup function:

cleanup () 
 rm -f "$tmpfile"
 rm -rf "$tmpdir"


tmpdir=$(mktemp -d)
tmpfile=$(mktemp)

trap cleanup EXIT

# The rest of the script goes here.

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

edited 1 hour ago

answered 2 hours ago

Kusalananda

113k15217345

answered 2 hours ago

Kusalananda

113k15217345

answered 2 hours ago

Kusalananda

113k15217345

add a commentÂ |Â

up vote
1
down vote

Write a shell-function that will be executed when your script if finished. In the example below I call it 'cleanup' and set a trap to be executed on exit levels 1 2 3 6

trap cleanup 0 1 2 3 6

cleanup()

 [ -d $TMP ] && rm -rf $TMP

See this post for more info.

answered 2 hours ago

Dirk Krijgsman

4546

add a commentÂ |Â

up vote
1
down vote

Write a shell-function that will be executed when your script if finished. In the example below I call it 'cleanup' and set a trap to be executed on exit levels 1 2 3 6

trap cleanup 0 1 2 3 6

cleanup()

 [ -d $TMP ] && rm -rf $TMP

See this post for more info.

answered 2 hours ago

Dirk Krijgsman

4546

add a commentÂ |Â

up vote
1
down vote

Write a shell-function that will be executed when your script if finished. In the example below I call it 'cleanup' and set a trap to be executed on exit levels 1 2 3 6

trap cleanup 0 1 2 3 6

cleanup()

 [ -d $TMP ] && rm -rf $TMP

See this post for more info.

answered 2 hours ago

Dirk Krijgsman

4546

Write a shell-function that will be executed when your script if finished. In the example below I call it 'cleanup' and set a trap to be executed on exit levels 1 2 3 6

trap cleanup 0 1 2 3 6

cleanup()

 [ -d $TMP ] && rm -rf $TMP

See this post for more info.

answered 2 hours ago

Dirk Krijgsman

4546

answered 2 hours ago

Dirk Krijgsman

4546

answered 2 hours ago

Dirk Krijgsman

4546

answered 2 hours ago

Dirk Krijgsman

4546

add a commentÂ |Â

up vote
1
down vote

You can chdir into it and then remove it, provided that you don't try to use paths inside it afterwards:

#! /bin/sh
dir=`mktemp -d`
cd "$dir"
exec 4>file 3<file
rm -fr "$dir"

echo yes >&4 # OK
cat <&3 # OK

cat file # FAIL
echo yes > file # FAIL

I haven't checked, but it's most probably the same problem when using openat(2) in C with a directory that no longer exists in the file system.

If you're root, you can play with a separate namespace, and mount -t tmpfs tmpfs /dir inside it.

The cannonical answers (set a trap on EXIT) don't work if your script is forced into an unclean exit (eg. with SIGKILL); that may leave sensitive data hanging around.

edited 17 mins ago

answered 59 mins ago

qubert

3955

add a commentÂ |Â

up vote
1
down vote

You can chdir into it and then remove it, provided that you don't try to use paths inside it afterwards:

#! /bin/sh
dir=`mktemp -d`
cd "$dir"
exec 4>file 3<file
rm -fr "$dir"

echo yes >&4 # OK
cat <&3 # OK

cat file # FAIL
echo yes > file # FAIL

I haven't checked, but it's most probably the same problem when using openat(2) in C with a directory that no longer exists in the file system.

If you're root, you can play with a separate namespace, and mount -t tmpfs tmpfs /dir inside it.

The cannonical answers (set a trap on EXIT) don't work if your script is forced into an unclean exit (eg. with SIGKILL); that may leave sensitive data hanging around.

edited 17 mins ago

answered 59 mins ago

qubert

3955

add a commentÂ |Â

up vote
1
down vote

You can chdir into it and then remove it, provided that you don't try to use paths inside it afterwards:

#! /bin/sh
dir=`mktemp -d`
cd "$dir"
exec 4>file 3<file
rm -fr "$dir"

echo yes >&4 # OK
cat <&3 # OK

cat file # FAIL
echo yes > file # FAIL

I haven't checked, but it's most probably the same problem when using openat(2) in C with a directory that no longer exists in the file system.

If you're root, you can play with a separate namespace, and mount -t tmpfs tmpfs /dir inside it.

The cannonical answers (set a trap on EXIT) don't work if your script is forced into an unclean exit (eg. with SIGKILL); that may leave sensitive data hanging around.

edited 17 mins ago

answered 59 mins ago

qubert

3955

You can chdir into it and then remove it, provided that you don't try to use paths inside it afterwards:

#! /bin/sh
dir=`mktemp -d`
cd "$dir"
exec 4>file 3<file
rm -fr "$dir"

echo yes >&4 # OK
cat <&3 # OK

cat file # FAIL
echo yes > file # FAIL

I haven't checked, but it's most probably the same problem when using openat(2) in C with a directory that no longer exists in the file system.

If you're root, you can play with a separate namespace, and mount -t tmpfs tmpfs /dir inside it.

The cannonical answers (set a trap on EXIT) don't work if your script is forced into an unclean exit (eg. with SIGKILL); that may leave sensitive data hanging around.

edited 17 mins ago

answered 59 mins ago

qubert

3955

edited 17 mins ago

answered 59 mins ago

qubert

3955

answered 59 mins ago

qubert

3955

answered 59 mins ago

qubert

3955

add a commentÂ |Â

Bob Johnson is a new contributor. Be nice, and check out our Code of Conduct.

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