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grep: Multiple files, other input

From: Unix for Mac OS X Users

Video: grep: Multiple files, other input

What if we want to grep from multiple files or search inside directories? There are a couple of ways to do it. One is we could just say well, grep for Apple inside and then provide the file path, a directory in this case. So let's just say we're going to use the current path. The dot represents the current path. We could just as easily type Users/Kevin /unix_files, same thing. It comes back and says I didn't find anything. It's because we've given it a directory. If we want it to do it in this way then we need to put the -R option in front of it for recursive.

grep: Multiple files, other input

What if we want to grep from multiple files or search inside directories? There are a couple of ways to do it. One is we could just say well, grep for Apple inside and then provide the file path, a directory in this case. So let's just say we're going to use the current path. The dot represents the current path. We could just as easily type Users/Kevin /unix_files, same thing. It comes back and says I didn't find anything. It's because we've given it a directory. If we want it to do it in this way then we need to put the -R option in front of it for recursive.

Recursively look inside here, meaning check all of the files that are in this directory and then go into the directories below that and look inside those and so on. The same option that we used with copy, move, and remove earlier. So grep recursively for apple inside this directory. So whenever we use a directory, we want to use -R just like we did when we were doing copying. So now it tells me not only the matches it made but the file where it occurs. We could also provide the -n option after that and now it gives me the line numbers in each of those files.

Notice that it does this by default. It says ah, now because I'm searching multiple files I'm not just going to give you the results. I'm going to tell where I found them as well. You can suppress that. Let's just erase all of this and I'll just use the dot from now on just because it's a little bit shorter and instead of the n option let's use the h option. h option will suppress the file name and still show you just the line itself or if you wanted the other way around and you wanted just the file name, you can use the l option. Now it tells me ah, I've found apple in three files.

Fruit, sorted fruit, and unique sorted fruit. That can be really handy. All right you could say all right, here are the relevant files I found them, and now we could presently pipe those results into something else, right. Maybe we want to now concatenate these three files. After we find them then we could potentially concatenate them together. If we want to do the opposite of that and find the files that don't have a match it's the capital L. So that returns all files that did not match. This is very similar to the -v option that we did earlier but that returned the lines that didn't match. This is returning whole files that don't match.

So it's similar but not the same. Now this recursive approach using this R option is searching all files in all directories. Don't forget that bash also lets us use wildcards to trend pick more specific files and that might speed up our searches. For example, just using ls we can do ls*.txt. And we can see just the text files that are in the current folder. Or even more specific, we can say all right let's check just the fruit files. All right, so now I'm saying just the fruit files. That wildcard lets us do that. That's handy with grep because now for example we can say we'll grep for apple inside just the files that end in fruit.txt. It's the same results that we got but it's just searching these three files instead of searching every file and directory.

If you have a lot of files and directories this can be a lot faster. But the main point is don't just choose recursive by default. Think about what you're really trying to accomplish and try and find the best way to do that. Now these are working with files and directories. We also can change our standard input. We can use piped input. We could for example do cat fruit.txt and pipe that into grep for Apple. That's still just working with a file though, right. It's just as easy to do it the other way. Well it's really more useful as with something like ps aux. You remember that that returns a list of all of our currently running processes. Well, we can grep that list. Let's grep for Terminal.

There is my entry for Terminal. I can now see what its ID number is. I can see how long it's been running. I can see how much memory it's taking up, all of that information just by grepping for only the line that contains Terminal. Or we could say all right, show me everything that has applications in it. So now all of my Mac applications will show up and I can see just those and not have to sort to that whole list of running processes. Another place it is useful with the history. So for example we'd say history and let's grep that for Unix files.

Every time that I've made reference to the Unix files directory, we also could then use this as shortcuts to be able to run those commands. We saw how to do that when working with our history. Let's try history and let's pipe that through grep nano and then pipe that into less. Now I only have a few but if you have a lot of these we now would have a paginated list of all the times that we've ever used nano. So piper history, filter out so that we get only lines that have nano in it, and then use less pagination.

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This video is part of

Image for Unix for Mac OS X Users
Unix for Mac OS X Users

82 video lessons · 25702 viewers

Kevin Skoglund
Author

 
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  1. 3m 57s
    1. Introduction
      1m 14s
    2. Using the exercise files
      2m 43s
  2. 32m 2s
    1. What is Unix?
      7m 27s
    2. The terminal application
      4m 23s
    3. Logging in and using the command prompt
      5m 19s
    4. Command structure
      5m 22s
    5. Kernel and shells
      5m 25s
    6. Unix manual pages
      4m 6s
  3. 15m 58s
    1. The working directory
      2m 49s
    2. Listing files and directories
      3m 59s
    3. Moving around the filesystem
      4m 58s
    4. Filesystem organization
      4m 12s
  4. 1h 4m
    1. Naming files
      5m 41s
    2. Creating files
      2m 19s
    3. Unix text editors
      6m 39s
    4. Reading files
      5m 35s
    5. Reading portions of files
      3m 27s
    6. Creating directories
      2m 40s
    7. Moving and renaming files and directories
      8m 32s
    8. Copying files and directories
      3m 7s
    9. Deleting files and directories
      3m 38s
    10. Finder aliases in Unix
      4m 10s
    11. Hard links
      5m 30s
    12. Symbolic links
      6m 36s
    13. Searching for files and directories
      6m 32s
  5. 34m 58s
    1. Who am I?
      4m 3s
    2. Unix groups
      1m 52s
    3. File and directory ownership
      6m 41s
    4. File and directory permissions
      4m 27s
    5. Setting permissions using alpha notation
      6m 49s
    6. Setting permissions using octal notation
      3m 49s
    7. The root user
      1m 57s
    8. sudo and sudoers
      5m 20s
  6. 52m 34s
    1. Command basics
      4m 4s
    2. The PATH variable
      4m 13s
    3. System information commands
      3m 40s
    4. Disk information commands
      6m 8s
    5. Viewing processes
      5m 0s
    6. Monitoring processes
      3m 36s
    7. Stopping processes
      3m 19s
    8. Text file helpers
      6m 50s
    9. Utility programs
      7m 28s
    10. Using the command history
      8m 16s
  7. 20m 39s
    1. Standard input and standard output
      1m 24s
    2. Directing output to a file
      4m 13s
    3. Appending to a file
      2m 44s
    4. Directing input from a file
      5m 28s
    5. Piping output to input
      4m 40s
    6. Suppressing output
      2m 10s
  8. 41m 28s
    1. Profile, login, and resource files
      9m 11s
    2. Setting command aliases
      6m 59s
    3. Setting and exporting environment variables
      4m 54s
    4. Setting the PATH variable
      6m 10s
    5. Configuring history with variables
      6m 17s
    6. Customizing the command prompt
      6m 5s
    7. Logout file
      1m 52s
  9. 1h 25m
    1. grep: Searching for matching expressions
      5m 21s
    2. grep: Multiple files, other input
      4m 28s
    3. grep: Coloring matched text
      2m 57s
    4. Introduction to regular expressions
      3m 22s
    5. Regular expressions: Basic syntax
      3m 19s
    6. Using regular expressions with grep
      5m 20s
    7. tr: Translating characters
      8m 17s
    8. tr: Deleting and squeezing characters
      5m 30s
    9. sed: Stream editor
      7m 45s
    10. sed: Regular expressions and back-references
      7m 8s
    11. cut: Cutting select text portions
      7m 42s
    12. diff: Comparing files
      4m 35s
    13. diff: Alternative formats
      4m 30s
    14. xargs: Passing argument lists to commands
      7m 25s
    15. xargs: Usage examples
      7m 59s
  10. 42m 25s
    1. Finder integration
      4m 45s
    2. Clipboard integration
      5m 5s
    3. Screen capture
      3m 42s
    4. Shut down, reboot, and sleep
      3m 34s
    5. Text to speech
      2m 36s
    6. Spotlight integration: Searching metadata
      3m 41s
    7. Spotlight integration: Metadata attributes
      4m 24s
    8. Using AppleScript
      5m 23s
    9. System configurations: Viewing and setting
      5m 51s
    10. System configurations: Examples
      3m 24s
  11. 1m 26s
    1. Conclusion
      1m 26s

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