Open file starting at line number

[DanielCardonaRojas]

First of all great work! Loving this CLI

I checked the man page and did not see an option to open a file starting a line number, otherwise if
this feature does exist please document.

[Kienyew]

I think there's a --line-range option in bat, which might does what you need 😄

...
       -r, --line-range <N:M>...

              Only print the specified range of lines for each file. For example:

              --line-range 30:40
                     prints lines 30 to 40

              --line-range :40
                     prints lines 1 to 40

              --line-range 40:
                     prints lines 40 to the end of the file
...

[DanielCardonaRojas]

Kind of does but does not let scroll to lines previous to start of range.

[sharkdp]

You can try to use --pager=… to pass explicit options to less. Something like:

bat --pager="less -FR +10" src/assets_metadata.rs

You will need to add an offset of 3 lines for the bat header.

[Andriamanitra]

It would be beneficial if bat let line offset arguments pass through to less (or another pager, I think all of the most common ones use similar line offset argument syntax). This would allow users to easily get syntax highlighting from bat when an external program runs a command like $PAGER +263 /foo/bar/baz.

I specifically ran into this issue with Julia's less function -- as it stands you'd need to set $PAGER to quite an impressive bash spell in order to make this work.

[sontek]

@sharkdp That doesn't seem to work:

rg --vimgrep _files | fzf --delimiter=: --preview='bat --color always -H {2} --pager "less -RF +{2}" {1}'

Page never jumps down to the line needed to start at. {2} is the correct line number because -H does work

[sharkdp]

If you run that with a echo in front of the bat command, you can see what the problem is. This calls less with something like

less -RF +'17'

because fzf seems to include these single quotes. Unfortunately, since there is the + in front, the whole +'17' string will be sent to less as an argument. This causes less to run the command '17' which does not scroll to line 17.

You somehow need to either teach fzf to skip adding these quotes. Or teach less to run you command anyway. I couldn't find a solution after a quick search.

[QuarticCat]

It seems that --pager="less -FR +10" cannot correctly handle wrappings. When there are wrapping lines, less jumps to a wrong position. This also happens when we want to set line offset in fzf because fzf doesn't know what is the actual "line". We still need a starting line number flag.

[sharkdp]

When there are wrapping lines, less jumps to a wrong position. This also happens when we want to set line offset in fzf because fzf doesn't know what is the actual "line". We still need a starting line number flag.

Fair point. If we would add a feature like --scroll-to <LINE>, that would be less-specific. So far, we have avoided pager-specific features. Or do you have any other ideas on how to implement this?

[QuarticCat]

@sharkdp Can we pass the calculated line number to the --pager flag like fzf? For example, --pager="less -FR +{l}".

[sharkdp]

That sounds like a cool idea. Maybe there would be more variables that could be useful:

• {effective-scroll-line} for the bat-computed LINE that needs to be passed to the +… command
• {scroll-line} for the actual user-provided <LINE> argument
• {file-name}
• {detected-syntax}
• …

However, how can we provide this feature by default? We would need to modify the default value for --pager to be something like

less --other --default --options +{effective-scroll-line}

But what if --scroll-to isn't used? Should we simply set effective-scroll-line = 0? What other side-effects would this have?

Also, this would require every bat user with a custom --pager command in their config to now add the new +{effective-scroll-line} argument to make --scroll-to work.

If we don't add +{effective-scroll-line} by default, users of --scroll-to would be required to specify --pager="… +{effective-scroll-line}" themselves.

[QuarticCat]

@sharkdp I have another proposal: make the content of --pager flag a shell script statement, and provide those variables as environment variables, so that we don't need to create one more DSL to deal with complex situations.

For example, bat --pager='less -FR ${line:++$line}'. When $line is set, this is equivalent to bat --pager='less -FR +$line'. Otherwise, this is equivalent to bat --pager='less -FR '. We can also give $line a default value 0 or 1, which will make the default --pager flag simpler. If someone's pager cannot handle these values, he can use shell script to solve this problem.

As far as I know, the configuration of fzf-tab is done this way. See https://github.com/Aloxaf/fzf-tab/wiki/Configuration

Also, this would require every bat user with a custom --pager command in their config to now add the new +{effective-scroll-line} argument to make --scroll-to work.

Maybe we can add some hints to the help message of --scroll-to to reduce confusion. Besides, if the shell that executes the pager command is fixed, it is possible to detect which variables are set but not used and prompt some warnings. But I rather not do that.