5 ms·

[ is part of Bash syntax

frou_dh 12y ago
...and perhaps surprisingly also a program sitting on disk. $ type [ [ is a shell builtin $ [ 1 -gt 0 bash: [: missing `]' $ whereis [ /bin/[ $ /bin/[ 1 -gt 0 # success
- mappu 12y ago
  You got a root shell out of `/bin/[` ? Impressive :)
- e12e 12y ago
  Hm, which version of [ is that? I get: $ /usr/bin/[ 1 -gt 0 && echo success /usr/bin/[: missing `]' $ /usr/bin/[ 1 -gt 0 ] && echo success success (This is from coreutils 8.13-3.5 on Debian GNU/Linux)
  - frou_dh 12y ago
    What ships in OS X 10.9, presumably BSD-derived.
embolalia 12y ago
Nooo! Mistake #0 about shell scripting is thinking [ is syntax. It makes it way more weird and inexplicable. [ is a command, just like any other. That's why there needs to be a space between it and the next thing, and why you have to use weird looking flags and such. This is why I prefer the command `test`. It does the same thing as `[`, but is more obviously a command. And when you see it as a command, it's obvious that any command can be used in an if directly; if is just checking the exit code. (Whenever I see someone doing `if [ $? -ne 0 ]`, it makes me cry.)
- manicdee 12y ago
  test is [
  - kl4m 12y ago
    Indeed, "test" is exactly like "[" except that it doesn't check that its last argument is a "]".
    - vacri 12y ago
      For some reason I've always been amused by "which [". The idea of 'punctuation' being a command or a filename is something that threw me.
- jsmeaton 12y ago
  I'll bite. What should we be using instead of `if [ $? -ne 0 ]`? Because that's pretty standard in my (admittedly very basic) bash.
  - schoen 12y ago
    Instead of somecommand if [ $? -ne 0 ]; then echo "it failed"; fi the parent commenter presumably wants to see if ! somecommand; then echo "it failed"; fi
    - viraptor 12y ago
      Or: somecommand || echo "it failed" if it's just one statement. There are some cases where it just looks more natural. For example: start_service || log "already started"
  - deleted 12y ago
    [deleted]
- JetSpiegel 12y ago
  > when you see it as a command, it's obvious that any command can be used in an if directly; if is just checking the exit code One of the best days of my life
deleted 12y ago
[deleted]

...and perhaps surprisingly also a program sitting on disk. $ type [ [ is a shell builtin $ [ 1 -gt 0 bash: [: missing `]' $ whereis [ /bin/[ $ /bin/[ 1 -gt 0 # success

mappu 12y ago
You got a root shell out of `/bin/[` ? Impressive :)
e12e 12y ago
Hm, which version of [ is that? I get: $ /usr/bin/[ 1 -gt 0 && echo success /usr/bin/[: missing `]' $ /usr/bin/[ 1 -gt 0 ] && echo success success (This is from coreutils 8.13-3.5 on Debian GNU/Linux)
- frou_dh 12y ago
  What ships in OS X 10.9, presumably BSD-derived.

embolalia 12y ago

Nooo! Mistake #0 about shell scripting is thinking [ is syntax. It makes it way more weird and inexplicable. [ is a command, just like any other. That's why there needs to be a space between it and the next thing, and why you have to use weird looking flags and such. This is why I prefer the command `test`. It does the same thing as `[`, but is more obviously a command. And when you see it as a command, it's obvious that any command can be used in an if directly; if is just checking the exit code. (Whenever I see someone doing `if [ $? -ne 0 ]`, it makes me cry.)

manicdee 12y ago
test is [
- kl4m 12y ago
  Indeed, "test" is exactly like "[" except that it doesn't check that its last argument is a "]".
  - vacri 12y ago
    For some reason I've always been amused by "which [". The idea of 'punctuation' being a command or a filename is something that threw me.
jsmeaton 12y ago
I'll bite. What should we be using instead of `if [ $? -ne 0 ]`? Because that's pretty standard in my (admittedly very basic) bash.
- schoen 12y ago
  Instead of somecommand if [ $? -ne 0 ]; then echo "it failed"; fi the parent commenter presumably wants to see if ! somecommand; then echo "it failed"; fi
  - viraptor 12y ago
    Or: somecommand || echo "it failed" if it's just one statement. There are some cases where it just looks more natural. For example: start_service || log "already started"
- deleted 12y ago
  [deleted]
JetSpiegel 12y ago
> when you see it as a command, it's obvious that any command can be used in an if directly; if is just checking the exit code One of the best days of my life

deleted 12y ago

[deleted]