I'm usually inside GNU Screen or tmux, and that doesn't give me great scrolling functionality. Is there an alternative to tail -f that allows me to quickly scroll up?
A tool that is like most is to less and more.
This question is related but far from specific. I'm really looking for something that lets me scroll.
You can use less +F to start less in its "forward forever" mode. In this mode, less will behave like tail -f, ignoring the ends of files and providing a steady stream of text.
When you want to scroll, press Ctrl+x¹. To re-enter forward forever mode, press Shift+f (i.e., capital ‘F’).
¹ Ctrl+c (or whatever sends SIGINT) also works but when less is used in a pipeline, that also has the side effect of killing all other commands in the pipeline, so Ctrl+x was introduced in later versions of less to avoid that.
Shift+F to resume (at least on my machine) --follow-name. So less --follow-name +F. This will cause less to periodically reopen the file as it follows. This extra option is not needed if the file you are following is being updated normally, but if instead of being updated normally, the file is instead being overwritten with a new file of the same name, then --follow-name will make it work as expected. Well you can use
tail -f <file> | less then you can have the best of both worlds!
less from reading from the pipe and restart the programs once he is done scrolling. I almost always use less for this sort of thing. I've never used the "forward forever" mode, instead I've got by just using less's runtime shortcuts for scrolling:-
< - Scroll to beginning of stream
> - Scroll to end of stream
Note, that if the buffer is read from a file, and that file has had new content appended to it since less was first opened, then the new content will be visible, the next time > is pressed, even when not in "forward forever" mode.
G to scroll to the end and g to scroll to the beginning, which is useful for vim-users. You can also use
watch -n 10 cat <file>
watch – execute a program periodically, showing output fullscreen
SYNOPSIS
watch [-dhvt] [-n <seconds>] [--differences[=cumulative]] [--help] [--interval=<seconds>] [--no-title] [--version] <command>DESCRIPTION
watchrunscommandrepeatedly, displaying its output (the first screenful). This allows you to watch the program output change over time. By default, the program is run every 2 seconds; use-nor--intervalto specify a different interval.The
-dor--differencesflag will highlight the differences between successive updates. The--cumulativeoption makes highlighting "sticky", presenting a running display of all positions that have ever changed. The-tor--no-titleoption turns off the header showing the interval, command, and current time at the top of the display, as well as the following blank line.
tmuxand intmuxyou can pressctrl+b, [to enter scroll mode. i'm sure you're aware. but many others may not be: depending on your term, you can then use pgup+pgdn and arrow keys to navigate the backlog, or scroll with your mouse; to exit scroll mode you pressq// you can continue usingtail -f, orless +F, orcator scroll an entire bash session for that matter.. it's rare to "need to" invokelessjust to scroll through a wall of text.tmuxhotkeys are "not that great" you may find how-can-i-page-up-or-down-in-tmux-with-terminal-app useful for customizing (or correcting) your configuration -- i've had bad (default) term configs that rendered extended keys useless.