6 ms·

My good old trick to mitigate that is: touch /-@ I also always do it in my home directory: touch ~/-@ That's the first thing I do on a new host. Wh

My good old trick to mitigate that is: touch /-@ I also always do it in my home directory: touch ~/-@ That's the first thing I do on a new host. When accidentally running rm -f *, the command expands to -@ first, which is not a valid option and makes the command fail before doing any harm rm: illegal option -- @ usage: rm [-f | -i] [-dPRrvW] file ...

ulrikrasmussen 12y ago
While this is a really nice hack, stuff like this is also the reason I feel really uneasy when writing shell scripts. What works now may suddenly break in the future due to inadequate escaping of filenames.
liviu- 12y ago
touch /-- rm -rf * (admittedly, this would be a malicious attempt rather than a careless bug)
miles 12y ago
Neat idea! Just tested that in an OS X 10.8 virtual machine; while it works nicely against "rm -rf *", sadly it does not help stop an accidental sudo rm -rf / or ~/. Also, "touch ~-@" created a file in the home directory called "~-@"; in order to set the correct filename, I cd'd into ~ and then ran "touch ./-@".
amadvance 12y ago
Likely you mean: touch ~/-@
atmosx 12y ago
Hm that's a cool trick. IIRC some distributions (Suse?) had a 'bash' clause where you couldn't do "rm -rf /" without 'y'. My 'zsh' has this one too, when I 'rm -rf /some/dir/' always asks if I'm "sure". Truth to be told, I'm not even expecting the text in "stdout" anymore, my finger goes to the 'y' automatically, which means that if I make something stupid it won't be able to protect me :-P The last couple of years I stopped doing 'stupid things' by stop working on the shell when I'm very tired. That was the cause of my rm-related-incidents in the past :-)
- iancarroll 12y ago
  Some versions of RM (Ubuntu/Debian if I remember correctly) require --no-preserve-root.
Aissen 12y ago
rm -rf -- $EMPTY_VAR/* Ooops.
lambeosaurus 12y ago
As someone who uses the commandline a lot but isn't exactly a wizard, why does this work?
- raverbashing 12y ago
  More specifically, it is expanded on the shell Example: $ echo /* /bin /boot /dev /etc /home (...)
- lsb 12y ago
  globbing expression expand to all the files that match. if a directory has 1.txt, 2.txt, and 3.txt then << rm * >> expands to "rm 1.txt 2.txt 3.txt" and is then executed. if you have -@, 1.txt, 2.txt, and 3.txt, that expands to << rm -@ 1.txt 2.txt 3.txt >>, and that can't execute. (if you really wanted to remove your -@ you'd do << rm -- * >> because a double-dash signals the end of command-line options.)
- ulrikrasmussen 12y ago
  The * is expanded by the shell to a space-delimited list of filenames, but the shell does not adequately escape filenames that can be misinterpreted as arguments to 'rm'.
  - gmac 12y ago
    That's kind of scary — in that case I guess I should avoid creating a file named -rf.
    - wodenokoto 12y ago
      That is really interesting. Can someone knowledgeable about the shell expand on this? I don't dare test it on my machine.
      - vbezhenar 12y ago
        Shell session to demonstrate (DO NOT DO IT IN THE DIRECTORY WITH IMPORTANT FILES): $ touch important $ chmod 400 important $ rm * override r-------- vbezhenar/staff for important? n $ touch -- -rf $ ls -l total 0 -rw-r--r-- 1 vbezhenar staff 0 Mar 24 14:35 -rf -r-------- 1 vbezhenar staff 0 Mar 24 14:35 important $ rm * $ ls -l total 0 -rw-r--r-- 1 vbezhenar staff 0 Mar 24 14:35 -rf $ rm -- -rf
JoshTriplett 12y ago
That won't actually help with rm -rf /* , only with rm -rf * in / or $HOME.
- hk__2 12y ago
  Would it work with `touch "/ -@"` (not the space)?
  - iso8859-1 12y ago
    how would changing the filename fix it? it's a hack relying on the globbing of the shell. if you're not using the globbing, the hack can never help you.
  - a3_nm 12y ago
    No, it doesn't work. "./*" expands to "./ -@" as a single field, which rm has no problems with. (Note that, however, this is still the globbing of the shell, as far as I understand.)
ioquatix 12y ago
Or just use zsh.
- michaelx386 12y ago
  Would zsh still protect me if the script explicitly uses Bash (i.e. #!/bin/bash)? Sorry if this is a dumb question, I'm unsure how shells work when calling other kinds of shell scripts.
  - phireal 12y ago
    No. If the script has the #! set as /bin/bash, then it will run as bash.
- anh79 12y ago
  zsh is an interactive shell. It is not to replace #bash as system shell as I know.
  - jedisct1 12y ago
    Zsh doesn't have to be used interactively. It's also excellent for scripting, and has far more features than bash.
Zenst 12y ago
Very handy trick. More so if no root access, myself I preer to rename rm and drop a shell wrapper in place and can be simply a case of changing all passed "" into "Sorry_Dave_I_can_not_allow_you_to_do_that" (or words to that effect) and all "-AsteRISKdeleteALL" into "-" and then that modified input is passed onto rm. But can adjust how and add rules to taste. That way the pain of having to type AsteRISKdeleteALL instead of * for rm events offsets any anxiety by far. You can also catch the rm and mv to a difectory with quota's you can call a recycle bin, some low end attached storage can be fine as well as not many situations when your wildcard deleting with a time factor. Can accommodate this in your own skulker to clean up in a more organised way overall in a timely manner. and and scripts you can path to the real rm command if needs be, last time I called it P45Generator, but not the finest for readability in any such scripts.
quoiquoi 12y ago
alias rm='trash-put'

ulrikrasmussen 12y ago

While this is a really nice hack, stuff like this is also the reason I feel really uneasy when writing shell scripts. What works now may suddenly break in the future due to inadequate escaping of filenames.

liviu- 12y ago

touch /-- rm -rf * (admittedly, this would be a malicious attempt rather than a careless bug)

miles 12y ago

Neat idea! Just tested that in an OS X 10.8 virtual machine; while it works nicely against "rm -rf *", sadly it does not help stop an accidental sudo rm -rf / or ~/. Also, "touch ~-@" created a file in the home directory called "~-@"; in order to set the correct filename, I cd'd into ~ and then ran "touch ./-@".

amadvance 12y ago

Likely you mean: touch ~/-@

atmosx 12y ago

Hm that's a cool trick. IIRC some distributions (Suse?) had a 'bash' clause where you couldn't do "rm -rf /" without 'y'. My 'zsh' has this one too, when I 'rm -rf /some/dir/' always asks if I'm "sure". Truth to be told, I'm not even expecting the text in "stdout" anymore, my finger goes to the 'y' automatically, which means that if I make something stupid it won't be able to protect me :-P The last couple of years I stopped doing 'stupid things' by stop working on the shell when I'm very tired. That was the cause of my rm-related-incidents in the past :-)

iancarroll 12y ago
Some versions of RM (Ubuntu/Debian if I remember correctly) require --no-preserve-root.

Aissen 12y ago

rm -rf -- $EMPTY_VAR/* Ooops.

lambeosaurus 12y ago

As someone who uses the commandline a lot but isn't exactly a wizard, why does this work?

raverbashing 12y ago
More specifically, it is expanded on the shell Example: $ echo /* /bin /boot /dev /etc /home (...)
lsb 12y ago
globbing expression expand to all the files that match. if a directory has 1.txt, 2.txt, and 3.txt then << rm * >> expands to "rm 1.txt 2.txt 3.txt" and is then executed. if you have -@, 1.txt, 2.txt, and 3.txt, that expands to << rm -@ 1.txt 2.txt 3.txt >>, and that can't execute. (if you really wanted to remove your -@ you'd do << rm -- * >> because a double-dash signals the end of command-line options.)
ulrikrasmussen 12y ago
The * is expanded by the shell to a space-delimited list of filenames, but the shell does not adequately escape filenames that can be misinterpreted as arguments to 'rm'.
- gmac 12y ago
  That's kind of scary — in that case I guess I should avoid creating a file named -rf.
  - wodenokoto 12y ago
    That is really interesting. Can someone knowledgeable about the shell expand on this? I don't dare test it on my machine.
    - vbezhenar 12y ago
      Shell session to demonstrate (DO NOT DO IT IN THE DIRECTORY WITH IMPORTANT FILES): $ touch important $ chmod 400 important $ rm * override r-------- vbezhenar/staff for important? n $ touch -- -rf $ ls -l total 0 -rw-r--r-- 1 vbezhenar staff 0 Mar 24 14:35 -rf -r-------- 1 vbezhenar staff 0 Mar 24 14:35 important $ rm * $ ls -l total 0 -rw-r--r-- 1 vbezhenar staff 0 Mar 24 14:35 -rf $ rm -- -rf

JoshTriplett 12y ago

That won't actually help with rm -rf /* , only with rm -rf * in / or $HOME.

hk__2 12y ago
Would it work with `touch "/ -@"` (not the space)?
- iso8859-1 12y ago
  how would changing the filename fix it? it's a hack relying on the globbing of the shell. if you're not using the globbing, the hack can never help you.
- a3_nm 12y ago
  No, it doesn't work. "./*" expands to "./ -@" as a single field, which rm has no problems with. (Note that, however, this is still the globbing of the shell, as far as I understand.)

ioquatix 12y ago

Or just use zsh.

michaelx386 12y ago
Would zsh still protect me if the script explicitly uses Bash (i.e. #!/bin/bash)? Sorry if this is a dumb question, I'm unsure how shells work when calling other kinds of shell scripts.
- phireal 12y ago
  No. If the script has the #! set as /bin/bash, then it will run as bash.
anh79 12y ago
zsh is an interactive shell. It is not to replace #bash as system shell as I know.
- jedisct1 12y ago
  Zsh doesn't have to be used interactively. It's also excellent for scripting, and has far more features than bash.

Zenst 12y ago

Very handy trick. More so if no root access, myself I preer to rename rm and drop a shell wrapper in place and can be simply a case of changing all passed "" into "Sorry_Dave_I_can_not_allow_you_to_do_that" (or words to that effect) and all "-AsteRISKdeleteALL" into "-" and then that modified input is passed onto rm. But can adjust how and add rules to taste. That way the pain of having to type AsteRISKdeleteALL instead of * for rm events offsets any anxiety by far. You can also catch the rm and mv to a difectory with quota's you can call a recycle bin, some low end attached storage can be fine as well as not many situations when your wildcard deleting with a time factor. Can accommodate this in your own skulker to clean up in a more organised way overall in a timely manner. and and scripts you can path to the real rm command if needs be, last time I called it P45Generator, but not the finest for readability in any such scripts.

quoiquoi 12y ago

alias rm='trash-put'