Programmer Humor @programming.dev chraebsli @programming.dev 8 mo. ago

Touch a file in Linux

94 comments

Does anyone actually use touch for its intended purpose? Must be up there with cat.
- TIL it's actually for changing timestamps.
  
  https://www.man7.org/linux/man-pages/man1/touch.1.html
  
  Wtf. All these years I thought 'touch' was reference to Michelangelo's Creation of Adam.
- The intended use of touch is to update the timestamp right?
  
  Yeah. It could just as well have issued a file not found error when you try to touch a nonexistent file. And we would be none the wiser about what we're missing in the world.
- We use it to trigger service restarts.
  
  touch tmp/service-restart.txt
  
  Using monit to detect the timestamp change and do the actual restart command.
  
  This is an interesting idea to allow non-root users to restart a service. It looks like this is doable with systemd too. https://superuser.com/a/1531261
- what is cat's use if not seeing whats inside a file?
  
  It is short for concatenate, which is to join things together. You can give it multiple inputs and it will output each one directly following the previous. It so happens to also work with just one input.
  
  It is to use along with split. e.g.
  
  You take a single large file, say 16GB
  
  Use split to break it into multiple files of 4GB
  
  Now you can transfer it to a FAT32 Removable Flash Drive and transfer it to whatever other computer that doesn't have Ethernet.
  
  Here, you can use cat to combine all files into the original file. (preferably accompanied by a checksum)
- I sometimes use cat to concatenate files. For example, add a header to a csv file without manually copy and paste it. It’s rare, but at least more frequent than using touch.
  
  $ cat file1 > output_file $ cat file2 >> output_file $ cat file3 >> output_file
  
  I'm sorry!
  
  That's its intended purpose - combining files together (the opposite of split). See the first line of the man page: https://man7.org/linux/man-pages/man1/cat.1.html
- When you updated a Django server, you were supposed to touch the settings.py file so the server would know to reload your code. (I haven't used any for a long time, so I don't know if it's still the procedure.)
  
  There are many small things that use it.
  
  it now has a hot reload, How long ago were you using Django?
- cat
  
  Ahhhhh, fuck. I'm quite noob with linux. I got into some rabbit hole trying to read the docs. I found 2 man pages, one is cat(1) and the other cat(1p). Apparently the 1p is for POSIX.
  
  If someone could help me understand... As far as I could understand I would normally be concerned with (1), but what would I need to be doing to be affected by (1p)?
  
  The POSIX standard is more portable. If you are writing scripts for your system, you can use the full features in the main man pages. If you are writing code that you want to run on other Linux systems, maybe with reduced feature sets like a tiny embedded computer or alternates to gnu tools like alpine linux, or even other unixes like the BSDs, you will have a better time if you limit yourself to POSIX-compatible features and options -- any POSIX-compatible Unix-like implementation should be able to run POSIX-compliant code.
  
  This is also why many shell scripts will call #!/bin/sh instead of #!/bin/bash -- sh is more likely to be available on tinier systems than bash.
  
  If you are just writing scripts and commands for your own purposes, or you know they will only be used on full-feature distributions, it's often simpler and more comfortable to use all of the advanced features available on your system.
  
  If you execute a binary without specifying the path to it, it will be searched from the $PATH environment variable, which is a list of places to look for the binary. From left to right, the first found one is returned.
  
  You can use which cat to see what it resolves to and whereis cat to get all possible results.
  
  If you intentionally wants to use a different binary with the same name, you can either directly use its path, or prepend its path to $PATH.
- I used it recently to update the creation date of a bunch of notes. Just wanted them to display in the correct order in Obsidian. Besides that though, always just used it for file creation lol
- I don't know anything about Linux but I do love touching cats
  
  You would love Linux cli.
- Cat is actually super useful.
- I mean, timestamps aren't really all that useful. Really just if you do some stuff with makefiles but even then it's a stretch. I did once use cat for its intended purpose tho, for a report. We split up the individual chapters into their own files so we have an easier time with git stuff, made a script that had an array with the files in the order we wanted, gave it to cat and piped that into pandoc
- Touch is super useful for commands that interact with a file but don't create the file by default. For example, yesterday I needed to copy a file to a remote machine accessible over ssh so I used scp (often known as "secure copy") but needed to touch the file in order to create it before scp would copy into it
  
  Sorry, what?
- Yes, Nextcloud can't sync files with a timestamp of 0
  
  Yup, stupid zip files and their directories from 1970
- I use it regularly
- Yes, when you are for example checking if the permissions in the directory are correct, or if you want to check if your nfs export is working. It's one of those commands that once you know it exists, you WILL find a way to use it.
  
  Well, those aren't really the intended use either.
- Creating an empty file is one of its intended purposes. Unix commands were designed as multi-purpose primitives, so they could be reused and composed to handle many different tasks. The touch command is no exception.
  
  https://www.youtube.com/watch?v=tc4ROCJYbm0&t=287s
- I use it all the time, especially in ssh on a server.
- i use both frequently but im also a pretty dumb user
These are some weird looking dolph--- oh
Remember to confirm consent before touching.
- You can only touch in places where you have permission to touch.
  
  sudo touch woman
Same energy as Joan Cornella's comics
- 'Murica!
Is there a command that's actually just for creating a new file?
- Nope. If you open a nonexistent path and you have permissions to write to that directory, then that file is created.
- I guess printf "" > file
  
  Feels dangerous to run. What happens if the file already exists and has something important in it?
  
  touch -a is probably better
- I mean, nano filename will work, but there's no mkfile that I can find...
  
  $>filename would also work, but it's not explicitly for creating a new file
- most shells will accept outputting from a silent command to a file, e.g. :> foo.txt (where : is the posix synonym to the true command)
- How often do you actually need a blank file though? Usually you'd be writing something in the file.
  
  I'm betting that's why none ever materialized. Most tools that can manipulate a file, can also create that file first, so there's just never been a usecase.
  
  Right-clicking the desktop to create a new txt file in Windows feels so natural, but I can't really think of any time you'd want to create a new file and do nothing with it in a CLI.
I'm way to used to doing nano file.txt that I always forget about touch.

Although most times, if I create a file, it's to put something in it
- If you need multiple files for testing a script or such: touch file{1..5}.txt
  
  If you're having a party or whatever: touch *
- I do the opposite, I forget I can just create a file with nano. I run touch then open it with nano after to edit.
  
  That's weird. Stop it.
- I usually do open filename because I prefer GUI text editors.
As a Linux user, that is truly magical, and beautiful.

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