reading_files.md

• cat: concatenate command

  • cat filename: shows content of the file
  • cat file1 file2: Shows both of the files as one

• wc: word count

  • wc -l file: returns line count of the file

• less: you can be page through big file with less

  • use pageup and pagedown
  • use / to search for word, hit n to go through the next matches
  • use ? to search for word backward, hit n to go through the next matches
  • use q to quit less.

• head: shows the top of the file

  • head filename
  • head -n 3 filename: shows the first 3 lines of the file

• tail: shows the bottom of the file

  • tail filename
  • tail -n 3 filename: shows the last 3 lines of the file

• sed: to edit files

  • sed -i: edit files in place
    • Example: sed -i '/^#/d;/^$/d' filename: remove (d) comments and empty lines from file
    • clean_file function takes the first arugment as the file namefunction clean_file { sed -i '/^#/d;/^$/d' $1}

• Comparing Files:

  • diff: Compare two files
    • Example: diff file1 file2, show the difference between file1 and file2
    • You can't compare binary files with diff
  • We can compare binary files using checksums

• Finding Files:

  • find: used to fine files
    • Example: find /usr/share/doc/ -name '*.pdf' search recursively for pdf files
    • We can execute a commands on found files
      • find /usr/share/doc/ -name '*.pdf' -exec cp {} . \;, copies pdf file found to current dir
      • find -name '*.pdf' -delete: delete all found files in the current directory (default dir).
    • We can search by file type:
      • find /etc/ -type l: Searches for files of type symbolic link
    • We can specify level of the search with -maxdepth
      • find /etc/ -maxdepth 1 -type l
    • We can search by size
      • find /boot -size +10000k -type f -exec du -h {} \;: find files bigger than 10mb of regular type and show disk usage in human readable format