4 ms·

> sponge: soak up standard input and write to a file How does this differ than just redirecting to a file in the shell?

cgag 10y ago
If you do something like: echo "hello world" >> dummyfile cat dummyfile | sed 's/hello/goodbye/' > dummyfile dummyfile will be blank afterwards if you do: cat dummyfile | sed 's/hello/goodbye/' | sponge dummyfile It'll work as you'd expect (or at least as I'd expect). Otherwise `> dummyfile` will truncate dummyfile before it's read and inputed into sed.
- bluejekyll 10y ago
  Ah, yes. I like it. I've definitely made the exact mistake you point out. Thanks!
  - cgag 10y ago
    I actually think I learned about sponge after I burned myself with this same mistake.
- StillBored 10y ago
  For the sed example, what you actually want is -i which modifies the given file. AKA sed -i 's/hello/goodby/' dummyfile
  - phamilton 10y ago
    That's only in gnu coreutils. BSD coreutils don't support -i
    - cheiVia0 10y ago
      didn't https://www.freebsd.org/cgi/man.cgi?query=sed https://www.freebsd.org/cgi/man.cgi?query=sed http://man.openbsd.org/OpenBSD-current/man1/sed.1 http://man.openbsd.org/OpenBSD-current/man1/sed.1 http://netbsd.gw.com/cgi-bin/man-cgi?sed++NetBSD-current http://netbsd.gw.com/cgi-bin/man-cgi?sed++NetBSD-current
      - deleted 10y ago
        [deleted]
- mfontani 10y ago
  Isn't that what `tee` does, minus the "also displaying on STDOUT" bit?
  - FreeFull 10y ago
    tee doesn't store all the input before writing as far as I know, so it wouldn't work either in this case.
- Chris2048 10y ago
  Is this true? I though the issue was that the write might happen while the file is still being read? Does the '>' operator blanks the file first, before the read happens?
  - ferrari8608 10y ago
    > erases the file first and >> appends without erasing This isn't the issue.
parenthephobia 10y ago
sponge only writes the file once all input has been read, and - if the file already exists - tries to do the operation atomically by writing to a temporary file and renaming it over the old file.

cgag 10y ago

If you do something like: echo "hello world" >> dummyfile cat dummyfile | sed 's/hello/goodbye/' > dummyfile dummyfile will be blank afterwards if you do: cat dummyfile | sed 's/hello/goodbye/' | sponge dummyfile It'll work as you'd expect (or at least as I'd expect). Otherwise `> dummyfile` will truncate dummyfile before it's read and inputed into sed.

bluejekyll 10y ago
Ah, yes. I like it. I've definitely made the exact mistake you point out. Thanks!
- cgag 10y ago
  I actually think I learned about sponge after I burned myself with this same mistake.
StillBored 10y ago
For the sed example, what you actually want is -i which modifies the given file. AKA sed -i 's/hello/goodby/' dummyfile
- phamilton 10y ago
  That's only in gnu coreutils. BSD coreutils don't support -i
  - cheiVia0 10y ago
    didn't https://www.freebsd.org/cgi/man.cgi?query=sed https://www.freebsd.org/cgi/man.cgi?query=sed http://man.openbsd.org/OpenBSD-current/man1/sed.1 http://man.openbsd.org/OpenBSD-current/man1/sed.1 http://netbsd.gw.com/cgi-bin/man-cgi?sed++NetBSD-current http://netbsd.gw.com/cgi-bin/man-cgi?sed++NetBSD-current
    - deleted 10y ago
      [deleted]
mfontani 10y ago
Isn't that what `tee` does, minus the "also displaying on STDOUT" bit?
- FreeFull 10y ago
  tee doesn't store all the input before writing as far as I know, so it wouldn't work either in this case.
Chris2048 10y ago
Is this true? I though the issue was that the write might happen while the file is still being read? Does the '>' operator blanks the file first, before the read happens?
- ferrari8608 10y ago
  > erases the file first and >> appends without erasing This isn't the issue.

parenthephobia 10y ago

sponge only writes the file once all input has been read, and - if the file already exists - tries to do the operation atomically by writing to a temporary file and renaming it over the old file.