4

I would like to display as much from a file as possible which still fits in the terminal window, i.e. like a head with a dynamic number of lines.

If there are no lines which wrap to multiple lines and the prompt takes a single line then I can achieve that with head -n $(($(tput lines)-1)).

Is there a solution that doesn't require the assumptions above?

Edit: The solution should be non-interactive, so e.g. less doesn't work as far as I know.

Edit2: The solution should preferably also handle properly non-printing characters like ANSI escape sequences for text coloring.

Samuli Asmala
  • 186

2 Answers2

2

You can wrap with fold, then head it:

onepage () {
  fold -w "$(tput cols)" -s "$@" |
    head -n "$(($(tput lines)-1))"
}

Or maybe use pr. Assuming GNU pr:

pr -l "$((LINES - 1))" +1:1 -t
  • -l ... - set page height to $LINES - 1.
  • +1:1 start printing from the first page ... till the first page.
  • -t - don't print the header.
muru
  • 72,889
  • The first solution using fold and head works nicely expect when prompt is using more than one line. Is there a way to determine that from e.g. $PS1? The pr solution didn't work properly with lines which wrap to multiple lines. – Samuli Asmala Jul 08 '19 at 09:38
  • @SamuliAsmala not without expanding PS1 the way the shell expands it completely. If in bash, you could do something like foo=${PS1@P}; echo ${#foo} to get the length of the prompt, and then compare it with the width to see if it goes to multiple lines. (or maybe count lines in the expanded prompt) – muru Jul 08 '19 at 09:52
  • Your example doesn't work since I'm using .bash-git-prompt and my prompt is a bit more complicated: \[\033[0;32m\]✔\[\033[0;0m\] \[\033[0;33m\]\w\[\033[0;0m\] [\[\033[0;35m\]${GIT_BRANCH}\[\033[0;0m\] ↑·2\[\033[0;0m\]|\[\033[0;34m\]✚ 1\[\033[0;0m\]\[\033[1;34m\]⚑ 2\[\033[0;0m\]\[\033[0;0m\]] \n\[\033[0;37m\]$(date +%H:%M)\[\033[0;0m\] $ – Samuli Asmala Jul 08 '19 at 13:52
  • I also noticed that the fold solution doesn't work if there are non-printing characters like ANSI escape sequences for text coloring. There is a related question about Wrap text accounting for non-printing characters which is still unanswered. – Samuli Asmala Jul 08 '19 at 13:57
0

Perhaps use the program less

In the terminal, type:

less nameOfTheTextFile

And it will show all available lines that fit, starting from the first line of the text file

mrflash818
  • 305
  • 3
    less is interactive and doesn't return immediately back to prompt so unless there is a way to change that this method doesn't fit my needs. I've updated the question to be more clear on this. – Samuli Asmala Jul 08 '19 at 09:16