4 ms·

If you read, execute and understand all the code in "The Advanced Bash Scripting Guide", you will suddenly find yourself in the top 10% of people who use bash.

by beobab 7y ago

If you read, execute and understand all the code in "The Advanced Bash Scripting Guide", you will suddenly find yourself in the top 10% of people who use bash. https://www.tldp.org/LDP/abs/html/ https://www.tldp.org/LDP/abs/html/ (as a pdf: http://tldp.org/LDP/abs/abs-guide.pdf http://tldp.org/LDP/abs/abs-guide.pdf )

bryanrasmussen 7y ago
I'm pretty sure if you read, execute and understand all the code in most advanced guides to a language you will suddenly find yourself in the top 10% of the users of that language. But the understand is the hard part.
- deleted 7y ago
  [deleted]
obituary_latte 7y ago
Wonder why they advise cat /dev/null > file to empty a file rather than echo > file
- Dr_Emann 7y ago
  Because echo-ing into a file will make a file with 1 byte in it: a single newline character.
  - oreo83 7y ago
    echo -n >file
- chaosite 7y ago
  Well, `echo > file` won't empty the file, it will have a newline in it. At the very least you'll need `echo -n > file`.
  - luckman212 7y ago
    Trick: You can use just >file
  - leviathan 7y ago
    I've always done it as: `> file`
    - hultner 7y ago
      That's actually very nice, I never thought about that one.
    - hwj 7y ago
      Unfortunately, this doesn't work in fish: > fish: Expected a command, but instead found a redirection
      - danaur 7y ago
        Right but I don't think anyone is really concerned if it runs in fish. Fish is non standard and doesn't try to adhere to bash. If we want to write fish shell scripts we can do that elsewhere
        jgtrosh 7y ago
        Funny how the same sentence applies to bash wrt POSIX shell in other contexts
  - naniwaduni 7y ago
    Or after thinking about it for a moment, true > file. Or by its shorter name, :> file.
  - hultner 7y ago
    `printf > file`, but there's endless ways of achieving the same thing (and that's part of the beauty).
- TheSoftwareGuy 7y ago
  or why not `touch file`?
  - finnh 7y ago
    That works to create an empty file if none exists, but if the file already exists then 'touch' simply updates its atime/mtime and doesn't alter the contents. This latter effect is actually the purpose of touch; the file creation part is just a side effect.
- czr 7y ago
  IMO, the most natural method is simply: >file
- lasereyes136 7y ago
  This will empty a file without closing or invalidating any open file handlers so you can empty things like log files without restarting the services that are populating those files.
  - deleted 7y ago
    [deleted]
- harleypig 7y ago
  Or why they aren't recommending 'truncate -s 0 file'
aepiepaey 7y ago
The Bash Hackers Wiki is a much better resource, especially as reference material: https://wiki.bash-hackers.org/ https://wiki.bash-hackers.org/

by beobab 7y ago

bryanrasmussen 7y ago

I'm pretty sure if you read, execute and understand all the code in most advanced guides to a language you will suddenly find yourself in the top 10% of the users of that language. But the understand is the hard part.

deleted 7y ago
[deleted]

obituary_latte 7y ago

Wonder why they advise cat /dev/null > file to empty a file rather than echo > file

Dr_Emann 7y ago
Because echo-ing into a file will make a file with 1 byte in it: a single newline character.
- oreo83 7y ago
  echo -n >file
chaosite 7y ago
Well, `echo > file` won't empty the file, it will have a newline in it. At the very least you'll need `echo -n > file`.
- luckman212 7y ago
  Trick: You can use just >file
- leviathan 7y ago
  I've always done it as: `> file`
  - hultner 7y ago
    That's actually very nice, I never thought about that one.
  - hwj 7y ago
    Unfortunately, this doesn't work in fish: > fish: Expected a command, but instead found a redirection
    - danaur 7y ago
      Right but I don't think anyone is really concerned if it runs in fish. Fish is non standard and doesn't try to adhere to bash. If we want to write fish shell scripts we can do that elsewhere
      - jgtrosh 7y ago
        Funny how the same sentence applies to bash wrt POSIX shell in other contexts
- naniwaduni 7y ago
  Or after thinking about it for a moment, true > file. Or by its shorter name, :> file.
- hultner 7y ago
  `printf > file`, but there's endless ways of achieving the same thing (and that's part of the beauty).
TheSoftwareGuy 7y ago
or why not `touch file`?
- finnh 7y ago
  That works to create an empty file if none exists, but if the file already exists then 'touch' simply updates its atime/mtime and doesn't alter the contents. This latter effect is actually the purpose of touch; the file creation part is just a side effect.
czr 7y ago
IMO, the most natural method is simply: >file
lasereyes136 7y ago
This will empty a file without closing or invalidating any open file handlers so you can empty things like log files without restarting the services that are populating those files.
- deleted 7y ago
  [deleted]
harleypig 7y ago
Or why they aren't recommending 'truncate -s 0 file'

aepiepaey 7y ago

The Bash Hackers Wiki is a much better resource, especially as reference material: https://wiki.bash-hackers.org/ https://wiki.bash-hackers.org/