The Archives

  • 27.Nov.09
    Ignoring an alias cmd, shell | rafacas | (3)
    Sometimes I want to ignore an alias. That might seem to make no sense because one of the reasons (the reason?) to use an alias (like ls='ls --color') is creating shortcuts. But, in some cases I need to use the real command, with its real output. In my case, it is because I share the same username with other people on some systems (yes, it is pretty awful, but that is another issue). To do this, precede the command with a backslash: '\'. For example: $ \ls Update: As loood has said in the comments, typing the command in quotes has the same ...
  • 25.Nov.09
    Comparing directories in local or remote hosts shell | rafacas | (0)
    I frequently need to compare two directories (with similar structures) to find different or new files. When I have to compare them locally, I use the diff command. $ ls test* test: file1 file2 file3 file4 file5 test.new: file1 file2 file3 file4 file5 file6 $ diff -qr test test.new Files test/file2 and test.new/file2 differ Files test/file4 and test.new/file4 differ Only in test.new: file6 The -q option tells diff to tell only whether the files differ and the -r option is for recursively comparing inside subdirectories. A more complicated problem arises when the comparation has to be done remotely, that is one of the directories is in another host (Samba, NFS, etc ...
  • 14.May.09
    Split a file shell | rafacas | (0)
    Sometimes you need split a file. For example, to send them attached to an email. For this, you can use the split command. $ split -b 1m big_file file_part_ In the example, the big_file size is 10MB, the -b option split the file in 1MB pieces, and the file_part_ is the name given to the different parts. $ ls file_part_* file_part_aa file_part_ac file_part_ae file_part_ag file_part_ai file_part_ab file_part_ad file_part_af file_part_ah file_part_aj All the files are 1MB long. For joining all the parts you can ...
  • 10.Feb.09
    Some xargs scripts, shell | pfortuny | (1)
    Rafacas has already mentioned it, but xargs is sometimes much more useful than what it looks like. Two examples come to mind: Way too many files for rm or ls. It may well happen that a script has generated more than 10000 files in the same directory (it was your friend, not you, I know). If you try and rm * in there, you will be in trouble. Ditto if you simply want to count them with ls | wc -l. However, the following works: $ find . -type f -print0 | xargs -0 ls | wc -l (or rm instead of ...
  • 17.Sep.08
    Time cmd | pfortuny | (0)
    $ time for i in `ls` ; do cat $i ; done Shows the 'real', 'user' and 'sys' time invested in the task.
  • 28.Aug.08
    Listing files ordered by date cmd | rafacas | (0)
    $ ls -lt Lists files ordered by date starting at the newest one.