tetra: Display output that fits to terminal screen

Detect available terminal lines and print only output
that fits on terminal.

This is enabled only when in periodical output with
cleared screen.

Signed-off-by: Jiri Olsa <[email protected]>

cmd/tetra/debug/progs.go

@@ -26,6 +26,7 @@ import (
 	"github.com/cilium/ebpf/link"
 	"github.com/spf13/cobra"
 	"golang.org/x/sys/unix"
+	"golang.org/x/term"
 )
 
 type prog struct {
@@ -233,13 +234,31 @@ func round(state map[uint32]*prog) error {
 	writer := tabwriter.NewWriter(os.Stdout, 0, 8, 1, '\t', tabwriter.AlignRight)
 	fmt.Fprintln(writer, "Ovh(%)\tId\tCnt\tTime\tName\tPin")
 
+	cnt := 0
+	lines := 0
+
+	if !cfg.noclr && !cfg.once {
+		// We have 3 header lines, so terminal smaller than that is too
+		// small to print anything meaningful
+		_, lines, _ = term.GetSize(0)
+		if lines < 4 {
+			return nil
+		}
+		lines = lines - 4
+	}
+
 	for _, ovh := range overheads {
 		p := ovh.p
-		fmt.Fprintf(writer, "%6.2f\t%d\t%d\t%d\t%s\t%s\n",
+		fmt.Fprintf(writer, "%6.2f\t%d\t%d\t%d\t%s\t%s",
 			ovh.pct, p.id, ovh.cnt, ovh.time, p.name, p.pin)
+
+		if lines != 0 && cnt == lines {
+			break
+		}
+		cnt++
+		fmt.Fprintf(writer, "\n")
 	}
 
-	fmt.Fprintln(writer)
 	writer.Flush()
 
 	// Remove stale programs from state map

go.mod

@@ -44,6 +44,7 @@ require (
 	go.uber.org/multierr v1.11.0
 	golang.org/x/sync v0.10.0
 	golang.org/x/sys v0.28.0
+	golang.org/x/term v0.27.0
 	golang.org/x/time v0.8.0
 	google.golang.org/grpc v1.69.0
 	google.golang.org/protobuf v1.35.2
@@ -155,7 +156,6 @@ require (
 	golang.org/x/mod v0.22.0 // indirect
 	golang.org/x/net v0.33.0 // indirect
 	golang.org/x/oauth2 v0.23.0 // indirect
-	golang.org/x/term v0.27.0 // indirect
 	golang.org/x/text v0.21.0 // indirect
 	golang.org/x/tools v0.27.0 // indirect
 	gomodules.xyz/jsonpatch/v2 v2.4.0 // indirect