interp: Add --value-output/-V option to do tovalue before output

Idea is to skip display so that JSON is outputted instead of showing tree and hexdump etc.

doc/usage.md

@@ -40,10 +40,21 @@ fq 'd({verbose: true})' file
 
 # JSON representation for whole file
 fq tovalue file
+# or use -V (--value-output) that does tovalue automatically
+fq -V . file
+# or -Vr if the value is a string and you want a "raw" string
+fq -Vr .path.to.string file
 # JSON but raw bit fields truncated
 fq -o bits_format=truncate tovalue file
 # JSON but raw bit fields as md5 hex string
 fq -o bits_format=md5 tovalue file
+# look up a path
+fq '.some[1].path' file
+# look up a path and output JSON
+fq -V '.some[1].path' file
+# can be a query that outputs multiple values
+# this outputs first and last value in .same array and .path, three values in total
+fq -V '.some[0,-1], .path' file
 
 # grep whole tree by value
 fq 'grep("^prefix")' file
@@ -73,7 +84,7 @@ fq -o force=true -d mp4 file.mp4
 
 ### CLI arguments
 
-Most of fq's CLI argument are borrowed from jq and works in the same way.
+Most of jq's CLI arguments work with fq. But here are some additional ones specific to fq:
 
 #### Decode format `--decode`, `-d NAME`
 
@@ -85,7 +96,7 @@ Force format to decode instead of probing.
 
 Start interactive REPL.
 
-Can be used with both no, one and multiple inputs, ex just `fq -i ` start a REPL with `null` input, `fq -i 123` with the number 123 as input, `fq -i . a b` with two files as input. Also works with `--slurp`.
+Can be used with no input, one and multiple inputs, for example just `fq -i ` starts a REPL with `null` input, `fq -i 123` with the number 123 as input, `fq -i . a b` with two files as input. This also works with `--slurp`. In the REPL it is also possible to start a sub-REPLs by ending a query with `<query> | repl`, use ctrl-D to exit the sub-REPL. The sub-REPL will evaluate separately on each output from the query it was started. Use `[<query>] | repl` if you want to "slurp" into an array.
 
 #### Set option `--options`,`-o KEY=VALUE|@PATH`
 
@@ -97,6 +108,10 @@ Can be used with both no, one and multiple inputs, ex just `fq -i ` start a REPL
 
 Specify a global option or a format option, ex: `-o decode_samples=false` would for some container decoders like `mp4` and `matroska` disable decoding of samples.
 
+#### Value output `--value-output`, `-V`
+
+Output JSON value instead of decode tree. Use `-Vr` if you want raw string (no quotes).
+
 ### Display output
 
 `display` or `d` is the main function for displaying values and is also the function that will be used if no other output function is explicitly used. If its input is a decode value it will output a dump and tree structure or otherwise it will output as JSON.

pkg/interp/help.jq

@@ -84,12 +84,12 @@ def _help($arg0; $topic):
       ( "Example usages:"
       , "  fq . file"
       , "  fq d file"
+      , "  fq -V '.path[1].value' file"
       , "  fq tovalue file"
       , "  fq -r to_toml file.yml"
       , "  fq -s -d html 'map(.html.head.title?)' *.html"
       , "  cat file.cbor | fq -d cbor torepr"
       , "  fq 'grep(\"^main$\") | parent' /bin/ls"
-      , "  fq -r 'grep_by(.protocol==\"icmp\").source_ip | tovalue' *.pcap"
       , "  fq -i"
       )
     elif . == "banner" then

pkg/interp/interp.jq

@@ -16,7 +16,7 @@ def display($opts):
   ( . as $c
   | options($opts) as $opts
   | try _todisplay catch $c
-  | if _can_display then _display($opts)
+  | if ($opts.value_output | not) and _can_display then _display($opts)
     else
       ( if _is_string and $opts.raw_string then print
         else _print_color_json($opts)

pkg/interp/options.jq

@@ -65,6 +65,7 @@ def _opt_build_default_fixed:
       slurp:              false,
       string_input:       false,
       unicode:            ($stdout.is_terminal and env.CLIUNICODE != null),
+      value_output:       false,
       verbose:            false,
     }
   );
@@ -106,6 +107,7 @@ def _opt_options:
     slurp:              "boolean",
     string_input:       "boolean",
     unicode:            "boolean",
+    value_output:       "boolean",
     verbose:            "boolean",
     width:              "number",
   };
@@ -219,6 +221,11 @@ def _opt_eval($rest):
         else null
         end
       ),
+      value_output: (
+        if .value_output == true then true
+        else null
+        end
+      ),
     }
   | with_entries(select(.value != null))
   );
@@ -474,8 +481,8 @@ def _opt_cli_opts:
     },
     "raw_string": {
       short: "-r",
-      # for jq compat, is called raw string internally, "raw output" is if
-      # we can output raw bytes or not
+      # for jq compat, is called raw string internally, is different from "raw output" which
+      # is if we can output raw bytes or not
       long: "--raw-output",
       description: "Raw string output (without quotes)",
       bool: true
@@ -498,6 +505,12 @@ def _opt_cli_opts:
       description: "Force unicode output",
       bool: true
     },
+    "value_output": {
+      short: "-V",
+      long: "--value-output",
+      description: "Output JSON value (-Vr for raw string)",
+      bool: true
+    },
     "show_version": {
       short: "-v",
       long: "--version",

pkg/interp/testdata/args.fqtest

@@ -16,12 +16,12 @@ Usage: fq [OPTIONS] [--] [EXPR] [FILE...]
 Example usages:
   fq . file
   fq d file
+  fq -V '.path[1].value' file
   fq tovalue file
   fq -r to_toml file.yml
   fq -s -d html 'map(.html.head.title?)' *.html
   cat file.cbor | fq -d cbor torepr
   fq 'grep("^main$") | parent' /bin/ls
-  fq -r 'grep_by(.protocol=="icmp").source_ip | tovalue' *.pcap
   fq -i
 
 --arg NAME VALUE             Set variable $NAME to string VALUE
@@ -44,6 +44,7 @@ Example usages:
 --repl,-i                    Interactive REPL
 --slurp,-s                   Slurp all inputs into an array or string (-Rs)
 --unicode-output,-U          Force unicode output
+--value-output,-V            Output JSON value (-Vr for raw string)
 --version,-v                 Show version
 $ fq -i
 null> ^D
@@ -101,6 +102,7 @@ sizebase            10
 slurp               false
 string_input        false
 unicode             false
+value_output        false
 verbose             false
 width               135
 $ fq -X

pkg/interp/testdata/options.fqtest

@@ -86,6 +86,7 @@ $ fq -n options
   "slurp": false,
   "string_input": false,
   "unicode": false,
+  "value_output": false,
   "verbose": false,
   "width": 135
 }

pkg/interp/testdata/value_output.fqtest

@@ -0,0 +1,22 @@
+$ fq -V '.headers[0].header[]' test.mp3
+"ID3"
+4
+0
+{
+  "experimental_indicator": false,
+  "extended_header": false,
+  "unsynchronisation": false,
+  "unused": 0
+}
+35
+$ fq -Vr '.headers[0].header[]' test.mp3
+ID3
+4
+0
+{
+  "experimental_indicator": false,
+  "extended_header": false,
+  "unsynchronisation": false,
+  "unused": 0
+}
+35