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Can anyone explain why the command below produces the following error:

cannot open `{}' (No such file or directory)

Command

$ ls -al|grep -v '^d\|^$'|awk '{print $10}'|xargs file '{}'

I get the results I expected but with an error

{}:          cannot open `{}' (No such file or directory)
cpuinfo:     empty
cygdrive:    symbolic link to /cygdrive
devices:     empty
filesystems: empty
loadavg:     empty
meminfo:     empty
misc:        empty
mounts:      symbolic link to self/mounts
partitions:  empty
self:        symbolic link to 19812
stat:        empty
swaps:       empty
uptime:      empty
version:     empty
  • Because you didn't tell xargs to use {} as the replace-str? xargs -I {} .... BTW what are you trying to do, exactly? Parsing the output of ls -al isn't very robust – steeldriver Jul 8 '16 at 14:01
  • for xarg, the {} construct is unnecessary. If you drop it, your command might work, if the rest of it is sound. find ./ -type f | xargs file is a better suited command to what I think it is that you are trying to do, in my opinion – MelBurslan Jul 8 '16 at 14:01
  • Because column 10 is null/blank somewhere in you awk output. – ankidaemon Jul 8 '16 at 14:02
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    @MelBurslan: yes, and parsing of ls -al always have unexpected behavior. we can't we sure at which column file-name/dir-name is. He should be using find instead. – ankidaemon Jul 8 '16 at 14:09
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    find . -maxdepth 1 -type f -exec file {} + seems to work for me in Cygwin64 – steeldriver Jul 8 '16 at 14:40
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Because you're using xargs wrong, you've probably been inspired by how find works.

xargs takes the input and splits it into pieces to produce few commands, but (unless you've asked it into) it gives multiple arguments at the end of the command you secify after xargs, so your {} is just a part of the command. So you end up executing file {} <file_1> <file_2> ... <file_n>, file {} <file_n+1>..., .... (In your case you have so few files that only one command is executed.)

As you don't have a file called {}, file tells you so.

  • It not about the wrong use of xargs. Splitting of ls -al output is wrong. this should not be the way to split ls -al. He is getting the error because of null/blank in output of awk. – ankidaemon Jul 8 '16 at 14:08
  • I agree that the spliting of ls -al output is wrong, but that error also occurs in a directory where everything is simple enough not to trigger the problems with the splitting (if I change $10 to $9, but that might be his ls that is aliased to something weird). – Henrik - stop hurting Monica Jul 8 '16 at 14:35
  • I think it'd be worth mentioning -I, which lets you do exactly that, and is very useful if (for whatever reason) you need to put the arguments in the middle of your command. – Nic Hartley Jun 26 '18 at 21:30

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