[Search files] allow customizing the file preview command

README.md

@@ -130,15 +130,25 @@ They are always appended last to fzf's argument list. Because fzf uses the optio
 - [re-populate fzf's input list on demand](https://github.com/junegunn/fzf/issues/1750)
 - change the search mode
 
+### Change the command used to preview files
+
+The search directory feature, by default, uses `bat` to preview the contents of a file. `bat` is a well-adopted `cat` replacement with syntax highlighting, line numbers, and more. If you would like to change the preview tool (to `cat` for availability reasons, or to add custom logic like binary or image preview), you may set the `fzf_preview_file_cmd` variable. For example, in your `config.fish`, you may put:
+
+```fish
+set fzf_preview_file_cmd cat
+```
+
+Do not specify a target path in the command, as `fzf.fish` will [prepend the file][custom preview command] to preview to the command itself.
+
 ### Change the command used to preview folders
 
-The search directory feature, by default, uses `ls` to preview the contents of a directory. To integrate with the variety of `ls` replacements available, the command used to preview directories is configurable through the `fzf_preview_dir_cmd` variable. For example, in your `config.fish`, you may put:
+The search directory feature, by default, uses `ls` to preview the contents of a directory. To integrate with the variety of `ls` replacements available, the command used to preview directories is configurable through the `fzf_preview_dir_cmd` variable. Set `fzf_preview_dir_cmd` in your `config.fish` similar to the above.
 
 ```fish
 set fzf_preview_dir_cmd exa --all --color=always
 ```
 
-Do not specify a target path in the command, as `fzf.fish` will [prepend the directory][custom preview command] to preview to the command itself.
+As above, do not specify a target path in the command, as `fzf.fish` will [prepend the directory][custom preview command] to preview to the command itself.
 
 ### Change the files searched
 

functions/__fzf_preview_file.fish

@@ -5,10 +5,15 @@ function __fzf_preview_file --description "Print a preview for the given file ba
     set file_path $argv
 
     if test -f "$file_path" # regular file
-        bat --style=numbers --color=always "$file_path"
+        if set --query fzf_preview_file_cmd
+            # need to escape quotes to make sure eval receives file_path as a single arg
+            eval $fzf_preview_file_cmd \"$file_path\"
+        else
+            bat --style=numbers --color=always "$file_path"
+        end
     else if test -d "$file_path" # directory
         if set --query fzf_preview_dir_cmd
-            # need to escape quotes to make sure eval receives file_path as a single arg
+            # see above
             eval $fzf_preview_dir_cmd \"$file_path\"
         else
             # -A list hidden files as well, except for . and ..

tests/preview_file/custom_file_preview.fish

@@ -0,0 +1,6 @@
+set multi_word_dir "tests/_resources/multi word dir"
+
+set fzf_preview_file_cmd rev
+
+set actual (__fzf_preview_file "$multi_word_dir/file 1.txt")
+@test "correctly uses custom command to preview files" "$actual" = "1 elif si sihT"