diff --git a/docs/src/reference-verbs.md b/docs/src/reference-verbs.md
index 1a5c5eb21..5d5212f1a 100644
--- a/docs/src/reference-verbs.md
+++ b/docs/src/reference-verbs.md
@@ -1592,6 +1592,8 @@ Without -g, ceases consuming more input (i.e. is fast) when n records have been
Options:
-g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.
-n {n} Head-count to print. Default 10.
+ A negative count, e.g. -n -2, passes through all but the last n records,
+ optionally by category.
-h|--help Show this message.
@@ -1620,6 +1622,23 @@ zee eks 17 0.29081949506712723 0.054478717073354166
wye hat 24 0.7286126830627567 0.19441962592638418
+A negative count passes through all but the last *n* records, like GNU `head -n -n`:
+
+
+mlr --c2p head -n -2 example.csv
+
+
+color shape flag k index quantity rate
+yellow triangle true 1 11 43.6498 9.8870
+red square true 2 15 79.2778 0.0130
+red circle true 3 16 13.8103 2.9010
+red square false 4 48 77.5542 7.4670
+purple triangle false 5 51 81.2290 8.5910
+red square false 6 64 77.1991 9.5310
+purple triangle false 7 65 80.1405 5.8240
+yellow circle true 8 73 63.9785 4.2370
+
+
## histogram
@@ -3974,8 +3993,11 @@ a b c filename
Usage: mlr tail [options]
Passes through the last n records, optionally by category.
Options:
--g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.
--n {n} Head-count to print. Default 10.
+-g {a,b,c} Optional group-by-field names for tail counts, e.g. a,b,c.
+-n {n} Tail-count to print. Default 10.
+ A leading '+' means start at the nth record rather than print
+ the last n: e.g. -n +3 passes through all but the first 2
+ records, optionally by category.
-h|--help Show this message.
@@ -4002,6 +4024,23 @@ blue square 1 499872 0.618906 0.263796 0.531147 6.210738
yellow circle 1 499974 0.764951 0.252842 0.499699 5.013810
+As with GNU `tail`, a leading `+` starts at the *n*th record rather than printing the last *n* -- so `-n +3` passes through all but the first 2 records:
+
+
+mlr --c2p tail -n +3 example.csv
+
+
+color shape flag k index quantity rate
+red circle true 3 16 13.8103 2.9010
+red square false 4 48 77.5542 7.4670
+purple triangle false 5 51 81.2290 8.5910
+red square false 6 64 77.1991 9.5310
+purple triangle false 7 65 80.1405 5.8240
+yellow circle true 8 73 63.9785 4.2370
+yellow circle true 9 87 63.5058 8.3350
+purple square false 10 91 72.3735 8.2430
+
+
## tee
diff --git a/docs/src/reference-verbs.md.in b/docs/src/reference-verbs.md.in
index adedd4829..3003f48dc 100644
--- a/docs/src/reference-verbs.md.in
+++ b/docs/src/reference-verbs.md.in
@@ -543,6 +543,12 @@ GENMD-RUN-COMMAND
mlr --opprint head -n 1 -g b data/medium
GENMD-EOF
+A negative count passes through all but the last *n* records, like GNU `head -n -n`:
+
+GENMD-RUN-COMMAND
+mlr --c2p head -n -2 example.csv
+GENMD-EOF
+
## histogram
GENMD-RUN-COMMAND
@@ -1213,6 +1219,12 @@ GENMD-RUN-COMMAND
mlr --c2p tail -n 1 -g shape data/colored-shapes.csv
GENMD-EOF
+As with GNU `tail`, a leading `+` starts at the *n*th record rather than printing the last *n* -- so `-n +3` passes through all but the first 2 records:
+
+GENMD-RUN-COMMAND
+mlr --c2p tail -n +3 example.csv
+GENMD-EOF
+
## tee
GENMD-RUN-COMMAND
diff --git a/docs/src/streaming-and-memory.md b/docs/src/streaming-and-memory.md
index 01020b876..e1b0ad183 100644
--- a/docs/src/streaming-and-memory.md
+++ b/docs/src/streaming-and-memory.md
@@ -93,7 +93,7 @@ They are memory-friendly, and they don't wait for end of input to produce their
* [gap](reference-verbs.md#gap)
* [grep](reference-verbs.md#grep)
* [having-fields](reference-verbs.md#having-fields)
-* [head](reference-verbs.md#head)
+* [head](reference-verbs.md#head) -- if -n is non-negative
* [json-parse](reference-verbs.md#json-parse)
* [json-stringify](reference-verbs.md#json-stringify)
* [label](reference-verbs.md#label)
@@ -111,6 +111,7 @@ They are memory-friendly, and they don't wait for end of input to produce their
* [skip-trivial-records](reference-verbs.md#skip-trivial-records)
* [sort-within-records](reference-verbs.md#sort-within-records)
* [step](reference-verbs.md#step)
+* [tail](reference-verbs.md#tail) -- if invoked with -n +N (start-at-record-n form)
* [tee](reference-verbs.md#tee)
* [template](reference-verbs.md#template)
* [unflatten](reference-verbs.md#unflatten)
@@ -144,7 +145,8 @@ They are memory-unfriendly, and they wait for end of input to produce their outp
These retain a bounded number of records from one record to the next.
They are memory-friendly, but they wait for end of input to produce their output.
-* [tail](reference-verbs.md#tail)
+* [head](reference-verbs.md#head) -- if -n is negative
+* [tail](reference-verbs.md#tail) -- if not invoked with -n +N
* [top](reference-verbs.md#top)
## Non-streaming, retaining some state
diff --git a/docs/src/streaming-and-memory.md.in b/docs/src/streaming-and-memory.md.in
index 616a0cc52..07e3018dc 100644
--- a/docs/src/streaming-and-memory.md.in
+++ b/docs/src/streaming-and-memory.md.in
@@ -77,7 +77,7 @@ They are memory-friendly, and they don't wait for end of input to produce their
* [gap](reference-verbs.md#gap)
* [grep](reference-verbs.md#grep)
* [having-fields](reference-verbs.md#having-fields)
-* [head](reference-verbs.md#head)
+* [head](reference-verbs.md#head) -- if -n is non-negative
* [json-parse](reference-verbs.md#json-parse)
* [json-stringify](reference-verbs.md#json-stringify)
* [label](reference-verbs.md#label)
@@ -95,6 +95,7 @@ They are memory-friendly, and they don't wait for end of input to produce their
* [skip-trivial-records](reference-verbs.md#skip-trivial-records)
* [sort-within-records](reference-verbs.md#sort-within-records)
* [step](reference-verbs.md#step)
+* [tail](reference-verbs.md#tail) -- if invoked with -n +N (start-at-record-n form)
* [tee](reference-verbs.md#tee)
* [template](reference-verbs.md#template)
* [unflatten](reference-verbs.md#unflatten)
@@ -128,7 +129,8 @@ They are memory-unfriendly, and they wait for end of input to produce their outp
These retain a bounded number of records from one record to the next.
They are memory-friendly, but they wait for end of input to produce their output.
-* [tail](reference-verbs.md#tail)
+* [head](reference-verbs.md#head) -- if -n is negative
+* [tail](reference-verbs.md#tail) -- if not invoked with -n +N
* [top](reference-verbs.md#top)
## Non-streaming, retaining some state
diff --git a/pkg/lib/getoptify.go b/pkg/lib/getoptify.go
index 55d9d31aa..96435d479 100644
--- a/pkg/lib/getoptify.go
+++ b/pkg/lib/getoptify.go
@@ -26,8 +26,15 @@ func Getoptify(inargs []string) []string {
// Example: 'mlr unsparsify --fill-with -99999'.
outargs = append(outargs, inarg)
} else {
- for _, c := range inarg[1:] {
- outargs = append(outargs, "-"+string(c))
+ rest := inarg[1:]
+ for i := 0; i < len(rest); i++ {
+ // Pass integers without a leading dash, so that negative integers can be represented.
+ // Example: `head -n 4` and head -n4` can be differentiated from `head -n -4`.
+ if rest[i] >= '0' && rest[i] <= '9' {
+ outargs = append(outargs, rest[i:])
+ break
+ }
+ outargs = append(outargs, "-"+string(rest[i]))
}
}
} else if splitRegex.MatchString(inarg) {
diff --git a/pkg/transformers/head.go b/pkg/transformers/head.go
index 307f090c3..02c4b887b 100644
--- a/pkg/transformers/head.go
+++ b/pkg/transformers/head.go
@@ -28,6 +28,8 @@ func transformerHeadUsage(
fmt.Fprintf(o, "Options:\n")
fmt.Fprintf(o, "-g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.\n")
fmt.Fprintf(o, "-n {n} Head-count to print. Default 10.\n")
+ fmt.Fprintf(o, " A negative count, e.g. -n -2, passes through all but the last n records,\n")
+ fmt.Fprintf(o, " optionally by category.\n")
fmt.Fprintf(o, "-h|--help Show this message.\n")
}
@@ -68,16 +70,6 @@ func transformerHeadParseCLI(
}
headCount = n
- // This is a bit of a hack. In our Getoptify routine we preprocess
- // the command line sending '-xyz' to '-x -y -z', but leaving
- // '--xyz' as-is. Also, Unix-like tools often support 'head -n4'
- // and 'tail -n4' in addition to 'head -n 4' and 'tail -n 4'. Our
- // getoptify paradigm, combined with syntax familiar to users,
- // means we get '-n -4' here. So, take the absolute value to handle this.
- if headCount < 0 {
- headCount = -headCount
- }
-
} else if opt == "-g" {
names, err := cli.VerbGetStringArrayArg(verb, opt, args, &argi, argc)
if err != nil {
@@ -116,6 +108,7 @@ type TransformerHead struct {
recordTransformerFunc RecordTransformerFunc
unkeyedRecordCount int64
keyedRecordCounts map[string]int64
+ recordListsByGroup map[string]*[]*types.RecordAndContext
// See ChainTransformer
wroteDownstreamDone bool
@@ -126,15 +119,23 @@ func NewTransformerHead(
groupByFieldNames []string,
) (*TransformerHead, error) {
+ allButLast := headCount < 0
+ if allButLast {
+ headCount = -headCount
+ }
+
tr := &TransformerHead{
headCount: headCount,
groupByFieldNames: groupByFieldNames,
unkeyedRecordCount: 0,
keyedRecordCounts: make(map[string]int64),
+ recordListsByGroup: make(map[string]*[]*types.RecordAndContext),
wroteDownstreamDone: false,
}
- if groupByFieldNames == nil {
+ if allButLast {
+ tr.recordTransformerFunc = tr.transformAllButLast
+ } else if groupByFieldNames == nil {
tr.recordTransformerFunc = tr.transformUnkeyed
} else {
tr.recordTransformerFunc = tr.transformKeyed
@@ -207,3 +208,36 @@ func (tr *TransformerHead) transformKeyed(
*outputRecordsAndContexts = append(*outputRecordsAndContexts, inrecAndContext)
}
}
+
+func (tr *TransformerHead) transformAllButLast(
+ inrecAndContext *types.RecordAndContext,
+ outputRecordsAndContexts *[]*types.RecordAndContext, // list of *types.RecordAndContext
+ inputDownstreamDoneChannel <-chan bool,
+ outputDownstreamDoneChannel chan<- bool,
+) {
+ if !inrecAndContext.EndOfStream {
+ inrec := inrecAndContext.Record
+
+ groupingKey, ok := inrec.GetSelectedValuesJoined(tr.groupByFieldNames)
+ if !ok {
+ return
+ }
+
+ recordListForGroup := tr.recordListsByGroup[groupingKey]
+ if recordListForGroup == nil { // first time
+ recordListForGroup = &[]*types.RecordAndContext{}
+ tr.recordListsByGroup[groupingKey] = recordListForGroup
+ }
+
+ *recordListForGroup = append(*recordListForGroup, inrecAndContext)
+ for int64(len(*recordListForGroup)) > tr.headCount {
+ // Emit records that have fallen out of the window.
+ *outputRecordsAndContexts = append(*outputRecordsAndContexts, (*recordListForGroup)[0])
+ (*recordListForGroup)[0] = nil // release the backing-array slot's reference
+ *recordListForGroup = (*recordListForGroup)[1:]
+ }
+
+ } else {
+ *outputRecordsAndContexts = append(*outputRecordsAndContexts, inrecAndContext)
+ }
+}
diff --git a/pkg/transformers/tail.go b/pkg/transformers/tail.go
index 3f084c179..ddaf9edd1 100644
--- a/pkg/transformers/tail.go
+++ b/pkg/transformers/tail.go
@@ -26,8 +26,11 @@ func transformerTailUsage(
fmt.Fprintln(o, "Passes through the last n records, optionally by category.")
fmt.Fprintf(o, "Options:\n")
- fmt.Fprintf(o, "-g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.\n")
- fmt.Fprintf(o, "-n {n} Head-count to print. Default 10.\n")
+ fmt.Fprintf(o, "-g {a,b,c} Optional group-by-field names for tail counts, e.g. a,b,c.\n")
+ fmt.Fprintf(o, "-n {n} Tail-count to print. Default 10.\n")
+ fmt.Fprintf(o, " A leading '+' means start at the nth record rather than print\n")
+ fmt.Fprintf(o, " the last n: e.g. -n +3 passes through all but the first 2\n")
+ fmt.Fprintf(o, " records, optionally by category.\n")
fmt.Fprintf(o, "-h|--help Show this message.\n")
}
@@ -45,6 +48,7 @@ func transformerTailParseCLI(
argi++
tailCount := int64(10)
+ fromStart := false
var groupByFieldNames []string = nil
for argi < argc /* variable increment: 1 or 2 depending on flag */ {
@@ -62,22 +66,15 @@ func transformerTailParseCLI(
return nil, cli.ErrHelpRequested
} else if opt == "-n" {
+ if argi < argc && strings.HasPrefix(args[argi], "+") {
+ fromStart = true
+ }
n, err := cli.VerbGetIntArg(verb, opt, args, &argi, argc)
if err != nil {
return nil, err
}
tailCount = n
- // This is a bit of a hack. In our Getoptify routine we preprocess
- // the command line sending '-xyz' to '-x -y -z', but leaving
- // '--xyz' as-is. Also, Unix-like tools often support 'head -n4'
- // and 'tail -n4' in addition to 'head -n 4' and 'tail -n 4'. Our
- // getoptify paradigm, combined with syntax familiar to users,
- // means we get '-n -4' here. So, take the absolute value to handle this.
- if tailCount < 0 {
- tailCount = -tailCount
- }
-
} else if opt == "-g" {
names, err := cli.VerbGetStringArrayArg(verb, opt, args, &argi, argc)
if err != nil {
@@ -98,6 +95,7 @@ func transformerTailParseCLI(
transformer, err := NewTransformerTail(
tailCount,
+ fromStart,
groupByFieldNames,
)
if err != nil {
@@ -109,24 +107,43 @@ func transformerTailParseCLI(
type TransformerTail struct {
// input
- tailCount int64
+ count int64 // last-n count, or skip-count in from-start mode
groupByFieldNames []string
// state
+ recordTransformerFunc RecordTransformerFunc
// map from string to record slices
recordListsByGroup *lib.OrderedMap[*[]*types.RecordAndContext]
+ // for the from-start mode: per-group counts of records seen so far
+ countsByGroup map[string]int64
}
func NewTransformerTail(
tailCount int64,
+ fromStart bool,
groupByFieldNames []string,
) (*TransformerTail, error) {
tr := &TransformerTail{
- tailCount: tailCount,
groupByFieldNames: groupByFieldNames,
recordListsByGroup: lib.NewOrderedMap[*[]*types.RecordAndContext](),
+ countsByGroup: make(map[string]int64),
+ }
+
+ if fromStart {
+ // '-n +N' is a 1-based record index, i.e. skip the first n-1.
+ tr.count = tailCount - 1
+ if tr.count < 0 {
+ tr.count = 0
+ }
+ tr.recordTransformerFunc = tr.transformFromStart
+ } else {
+ if tailCount < 0 {
+ tailCount = -tailCount
+ }
+ tr.count = tailCount
+ tr.recordTransformerFunc = tr.transformLastN
}
return tr, nil
@@ -139,6 +156,15 @@ func (tr *TransformerTail) Transform(
outputDownstreamDoneChannel chan<- bool,
) {
HandleDefaultDownstreamDone(inputDownstreamDoneChannel, outputDownstreamDoneChannel)
+ tr.recordTransformerFunc(inrecAndContext, outputRecordsAndContexts, inputDownstreamDoneChannel, outputDownstreamDoneChannel)
+}
+
+func (tr *TransformerTail) transformLastN(
+ inrecAndContext *types.RecordAndContext,
+ outputRecordsAndContexts *[]*types.RecordAndContext, // list of *types.RecordAndContext
+ inputDownstreamDoneChannel <-chan bool,
+ outputDownstreamDoneChannel chan<- bool,
+) {
if !inrecAndContext.EndOfStream {
inrec := inrecAndContext.Record
@@ -155,7 +181,8 @@ func (tr *TransformerTail) Transform(
}
*recordListForGroup = append(*recordListForGroup, inrecAndContext)
- for int64(len(*recordListForGroup)) > tr.tailCount {
+ for int64(len(*recordListForGroup)) > tr.count {
+ (*recordListForGroup)[0] = nil // release the backing-array slot's reference
*recordListForGroup = (*recordListForGroup)[1:]
}
@@ -166,3 +193,28 @@ func (tr *TransformerTail) Transform(
*outputRecordsAndContexts = append(*outputRecordsAndContexts, inrecAndContext) // end-of-stream marker
}
}
+
+func (tr *TransformerTail) transformFromStart(
+ inrecAndContext *types.RecordAndContext,
+ outputRecordsAndContexts *[]*types.RecordAndContext, // list of *types.RecordAndContext
+ inputDownstreamDoneChannel <-chan bool,
+ outputDownstreamDoneChannel chan<- bool,
+) {
+ if !inrecAndContext.EndOfStream {
+ inrec := inrecAndContext.Record
+
+ groupingKey, ok := inrec.GetSelectedValuesJoined(tr.groupByFieldNames)
+ if !ok {
+ return
+ }
+
+ tr.countsByGroup[groupingKey]++
+ if tr.countsByGroup[groupingKey] > tr.count {
+ // Emit records now that we skipped the requested number of them.
+ *outputRecordsAndContexts = append(*outputRecordsAndContexts, inrecAndContext)
+ }
+
+ } else {
+ *outputRecordsAndContexts = append(*outputRecordsAndContexts, inrecAndContext) // end-of-stream marker
+ }
+}
diff --git a/test/cases/cli-help/0001/expout b/test/cases/cli-help/0001/expout
index 3911326be..70686675a 100644
--- a/test/cases/cli-help/0001/expout
+++ b/test/cases/cli-help/0001/expout
@@ -423,6 +423,8 @@ Without -g, ceases consuming more input (i.e. is fast) when n records have been
Options:
-g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.
-n {n} Head-count to print. Default 10.
+ A negative count, e.g. -n -2, passes through all but the last n records,
+ optionally by category.
-h|--help Show this message.
================================================================
@@ -1305,8 +1307,11 @@ tail
Usage: mlr tail [options]
Passes through the last n records, optionally by category.
Options:
--g {a,b,c} Optional group-by-field names for head counts, e.g. a,b,c.
--n {n} Head-count to print. Default 10.
+-g {a,b,c} Optional group-by-field names for tail counts, e.g. a,b,c.
+-n {n} Tail-count to print. Default 10.
+ A leading '+' means start at the nth record rather than print
+ the last n: e.g. -n +3 passes through all but the first 2
+ records, optionally by category.
-h|--help Show this message.
================================================================
diff --git a/test/cases/verb-head/0004/cmd b/test/cases/verb-head/0004/cmd
new file mode 100644
index 000000000..314fd3dbf
--- /dev/null
+++ b/test/cases/verb-head/0004/cmd
@@ -0,0 +1 @@
+mlr head -n -2 test/input/abixy-het
diff --git a/test/cases/verb-head/0004/experr b/test/cases/verb-head/0004/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-head/0004/expout b/test/cases/verb-head/0004/expout
new file mode 100644
index 000000000..99ddd9707
--- /dev/null
+++ b/test/cases/verb-head/0004/expout
@@ -0,0 +1,8 @@
+a=pan,b=pan,i=1,x=0.34679014,y=0.72680286
+a=eks,b=pan,i=2,x=0.75867996,y=0.52215111
+aaa=wye,b=wye,i=3,x=0.20460331,y=0.33831853
+a=eks,bbb=wye,i=4,x=0.38139939,y=0.13418874
+a=wye,b=pan,i=5,xxx=0.57328892,y=0.86362447
+a=zee,b=pan,i=6,x=0.52712616,y=0.49322129
+a=eks,b=zee,iii=7,x=0.61178406,y=0.18788492
+a=zee,b=wye,i=8,x=0.59855401,yyy=0.97618139
diff --git a/test/cases/verb-head/0005/cmd b/test/cases/verb-head/0005/cmd
new file mode 100644
index 000000000..ea16979e1
--- /dev/null
+++ b/test/cases/verb-head/0005/cmd
@@ -0,0 +1 @@
+mlr head -n -1 -g a test/input/abixy-het
diff --git a/test/cases/verb-head/0005/experr b/test/cases/verb-head/0005/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-head/0005/expout b/test/cases/verb-head/0005/expout
new file mode 100644
index 000000000..a2a235276
--- /dev/null
+++ b/test/cases/verb-head/0005/expout
@@ -0,0 +1,4 @@
+a=eks,b=pan,i=2,x=0.75867996,y=0.52215111
+a=eks,bbb=wye,i=4,x=0.38139939,y=0.13418874
+a=zee,b=pan,i=6,x=0.52712616,y=0.49322129
+a=pan,b=pan,i=1,x=0.34679014,y=0.72680286
diff --git a/test/cases/verb-head/0006/cmd b/test/cases/verb-head/0006/cmd
new file mode 100644
index 000000000..e6209d1c8
--- /dev/null
+++ b/test/cases/verb-head/0006/cmd
@@ -0,0 +1 @@
+mlr head -n3 test/input/abixy-het
diff --git a/test/cases/verb-head/0006/experr b/test/cases/verb-head/0006/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-head/0006/expout b/test/cases/verb-head/0006/expout
new file mode 100644
index 000000000..a996e619d
--- /dev/null
+++ b/test/cases/verb-head/0006/expout
@@ -0,0 +1,3 @@
+a=pan,b=pan,i=1,x=0.34679014,y=0.72680286
+a=eks,b=pan,i=2,x=0.75867996,y=0.52215111
+aaa=wye,b=wye,i=3,x=0.20460331,y=0.33831853
diff --git a/test/cases/verb-tail/0004/cmd b/test/cases/verb-tail/0004/cmd
new file mode 100644
index 000000000..38e0d1dc8
--- /dev/null
+++ b/test/cases/verb-tail/0004/cmd
@@ -0,0 +1 @@
+mlr tail -n +3 test/input/abixy-het
diff --git a/test/cases/verb-tail/0004/experr b/test/cases/verb-tail/0004/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-tail/0004/expout b/test/cases/verb-tail/0004/expout
new file mode 100644
index 000000000..9d21b60e3
--- /dev/null
+++ b/test/cases/verb-tail/0004/expout
@@ -0,0 +1,8 @@
+aaa=wye,b=wye,i=3,x=0.20460331,y=0.33831853
+a=eks,bbb=wye,i=4,x=0.38139939,y=0.13418874
+a=wye,b=pan,i=5,xxx=0.57328892,y=0.86362447
+a=zee,b=pan,i=6,x=0.52712616,y=0.49322129
+a=eks,b=zee,iii=7,x=0.61178406,y=0.18788492
+a=zee,b=wye,i=8,x=0.59855401,yyy=0.97618139
+aaa=hat,bbb=wye,i=9,x=0.03144188,y=0.74955076
+a=pan,b=wye,i=10,x=0.50262601,y=0.95261836
diff --git a/test/cases/verb-tail/0005/cmd b/test/cases/verb-tail/0005/cmd
new file mode 100644
index 000000000..a673a6355
--- /dev/null
+++ b/test/cases/verb-tail/0005/cmd
@@ -0,0 +1 @@
+mlr tail -n +2 -g a test/input/abixy-het
diff --git a/test/cases/verb-tail/0005/experr b/test/cases/verb-tail/0005/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-tail/0005/expout b/test/cases/verb-tail/0005/expout
new file mode 100644
index 000000000..f91a3cbd6
--- /dev/null
+++ b/test/cases/verb-tail/0005/expout
@@ -0,0 +1,4 @@
+a=eks,bbb=wye,i=4,x=0.38139939,y=0.13418874
+a=eks,b=zee,iii=7,x=0.61178406,y=0.18788492
+a=zee,b=wye,i=8,x=0.59855401,yyy=0.97618139
+a=pan,b=wye,i=10,x=0.50262601,y=0.95261836
diff --git a/test/cases/verb-tail/0006/cmd b/test/cases/verb-tail/0006/cmd
new file mode 100644
index 000000000..a84e13a49
--- /dev/null
+++ b/test/cases/verb-tail/0006/cmd
@@ -0,0 +1 @@
+mlr tail -n3 test/input/abixy-het
diff --git a/test/cases/verb-tail/0006/experr b/test/cases/verb-tail/0006/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-tail/0006/expout b/test/cases/verb-tail/0006/expout
new file mode 100644
index 000000000..d9b1a6092
--- /dev/null
+++ b/test/cases/verb-tail/0006/expout
@@ -0,0 +1,3 @@
+a=zee,b=wye,i=8,x=0.59855401,yyy=0.97618139
+aaa=hat,bbb=wye,i=9,x=0.03144188,y=0.74955076
+a=pan,b=wye,i=10,x=0.50262601,y=0.95261836
diff --git a/test/cases/verb-tail/0007/cmd b/test/cases/verb-tail/0007/cmd
new file mode 100644
index 000000000..f16b6d77e
--- /dev/null
+++ b/test/cases/verb-tail/0007/cmd
@@ -0,0 +1 @@
+mlr tail -n -2 test/input/abixy-het
diff --git a/test/cases/verb-tail/0007/experr b/test/cases/verb-tail/0007/experr
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/cases/verb-tail/0007/expout b/test/cases/verb-tail/0007/expout
new file mode 100644
index 000000000..a316396f7
--- /dev/null
+++ b/test/cases/verb-tail/0007/expout
@@ -0,0 +1,2 @@
+aaa=hat,bbb=wye,i=9,x=0.03144188,y=0.74955076
+a=pan,b=wye,i=10,x=0.50262601,y=0.95261836