nimgrep improvements (#12779)

* fix sticky colors in styledWrite

* nimgrep: context printing, colorthemes and other

* add context printing (lines after and before a match)
* nimgrep: add exclude/include options
* nimgrep: improve error printing & symlink handling
* nimgrep: rename dangerous `-r` argument
* add a `--newLine` style option for starting matching/context
  lines from a new line
* add color themes: 3 new themes besides default `simple`
* enable printing of multi-line matches with line numbers
* proper display of replace when there was another match replaced at
  the same line / context block
* improve cmdline arguments error reporting

1 files changed, 394 insertions, 97 deletions

diff --git a/tools/nimgrep.nim b/tools/nimgrep.nim
index 6121f1f19..7ba7e1f18 100644
--- a/tools/nimgrep.nim
+++ b/tools/nimgrep.nim
@@ -11,7 +11,7 @@ import
   os, strutils, parseopt, pegs, re, terminal
 
 const
-  Version = "1.4"
+  Version = "1.5"
   Usage = "nimgrep - Nim Grep Utility Version " & Version & """
 
   (c) 2012 Andreas Rumpf
@@ -19,12 +19,13 @@ Usage:
   nimgrep [options] [pattern] [replacement] (file/directory)*
 Options:
   --find, -f          find the pattern (default)
-  --replace, -r       replace the pattern
+  --replace, -!       replace the pattern
   --peg               pattern is a peg
   --re                pattern is a regular expression (default)
   --rex, -x           use the "extended" syntax for the regular expression
                       so that whitespace is not significant
-  --recursive         process directories recursively
+  --recursive, -r     process directories recursively
+  --follow            follow all symlinks when processing recursively
   --confirm           confirm each occurrence/replacement; there is a chance
                       to abort any time without touching the file
   --stdin             read pattern from stdin (to avoid the shell's confusing
@@ -32,10 +33,25 @@ Options:
   --word, -w          the match should have word boundaries (buggy for pegs!)
   --ignoreCase, -i    be case insensitive
   --ignoreStyle, -y   be style insensitive
-  --ext:EX1|EX2|...   only search the files with the given extension(s)
+  --ext:EX1|EX2|...   only search the files with the given extension(s),
+                      empty one ("--ext") means files with missing extension
+  --noExt:EX1|...     exclude files having given extension(s), use empty one to
+                      skip files with no extension (like some binary files are)
+  --includeFile:PAT   include only files whose names match the given regex PAT
+  --excludeFile:PAT   skip files whose names match the given regex pattern PAT
+  --excludeDir:PAT    skip directories whose names match the given regex PAT
   --nocolor           output will be given without any colours
   --color[:always]    force color even if output is redirected
-  --group             group matches by file
+  --colorTheme:THEME  select color THEME from 'simple' (default),
+                      'bnw' (black and white) ,'ack', or 'gnu' (GNU grep)
+  --afterContext:N,   
+               -a:N   print N lines of trailing context after every match
+  --beforeContext:N,
+               -b:N   print N lines of leading context before every match
+  --context:N, -c:N   print N lines of leading context before every match and
+                      N lines of trailing context after it
+  --group, -g         group matches by file
+  --newLine, -l       display every matching line starting from a new line
   --verbose           be verbose: list every processed file
   --filenames         find the pattern in the filenames, not in the contents
                       of the file
@@ -47,7 +63,7 @@ type
   TOption = enum
     optFind, optReplace, optPeg, optRegex, optRecursive, optConfirm, optStdin,
     optWord, optIgnoreCase, optIgnoreStyle, optVerbose, optFilenames,
-    optRex
+    optRex, optFollow
   TOptions = set[TOption]
   TConfirmEnum = enum
     ceAbort, ceYes, ceAll, ceNo, ceNone
@@ -61,8 +77,17 @@ var
   replacement = ""
   extensions: seq[string] = @[]
   options: TOptions = {optRegex}
+  skipExtensions: seq[string] = @[]
+  excludeFile: seq[Regex]
+  includeFile: seq[Regex]
+  excludeDir: seq[Regex]
   useWriteStyled = true
-  oneline = false
+  oneline = true
+  linesBefore = 0
+  linesAfter = 0
+  linesContext = 0
+  colorTheme = "simple"
+  newLine = false
 
 proc ask(msg: string): string =
   stdout.write(msg)
@@ -79,63 +104,262 @@ proc confirm: TConfirmEnum =
     of "e", "none": return ceNone
     else: discard
 
-proc countLines(s: string, first, last: int): int =
+func countLineBreaks(s: string, first, last: int): int =
+  # count line breaks (unlike strutils.countLines starts count from 0)
   var i = first
   while i <= last:
-    if s[i] == '\13':
+    if s[i] == '\c':
       inc result
-      if i < last and s[i+1] == '\10': inc(i)
-    elif s[i] == '\10':
+      if i < last and s[i+1] == '\l': inc(i)
+    elif s[i] == '\l':
       inc result
     inc i
 
-proc beforePattern(s: string, first: int): int =
-  result = first-1
-  while result >= 0:
-    if s[result] in Newlines: break
-    dec(result)
+func beforePattern(s: string, pos: int, nLines = 1): int =
+  var linesLeft = nLines
+  result = min(pos, s.len-1)
+  while true:
+    while result >= 0 and s[result] notin {'\c', '\l'}: dec(result)
+    if result == -1: break
+    if s[result] == '\l':
+      dec(linesLeft)
+      if linesLeft == 0: break
+      dec(result)
+      if result >= 0 and s[result] == '\c': dec(result)
+    else: # '\c'
+      dec(linesLeft)
+      if linesLeft == 0: break
+      dec(result)
   inc(result)
 
-proc afterPattern(s: string, last: int): int =
-  result = last+1
-  while result < s.len:
-    if s[result] in Newlines: break
-    inc(result)
+proc afterPattern(s: string, pos: int, nLines = 1): int =
+  result = max(0, pos)
+  var linesScanned = 0
+  while true:
+    while result < s.len and s[result] notin {'\c', '\l'}: inc(result)
+    inc(linesScanned)
+    if linesScanned == nLines: break
+    if result < s.len:
+      if s[result] == '\l':
+        inc(result)
+      elif s[result] == '\c':
+        inc(result)
+        if result < s.len and s[result] == '\l': inc(result)
+    else: break
   dec(result)
 
-proc writeColored(s: string) =
+template whenColors(body: untyped) =
   if useWriteStyled:
-    terminal.writeStyled(s, {styleUnderscore, styleBright})
+    body
   else:
     stdout.write(s)
 
-proc highlight(s, match, repl: string, t: tuple[first, last: int],
-               filename:string, line: int, showRepl: bool) =
-  const alignment = 6
-  if oneline:
-    stdout.write(filename, ":", line, ": ")
+proc printFile(s: string) =
+  whenColors:
+    case colorTheme
+    of "simple": stdout.write(s)
+    of "bnw": stdout.styledWrite(styleUnderscore, s)
+    of "ack": stdout.styledWrite(fgGreen, s)
+    of "gnu": stdout.styledWrite(fgMagenta, s)
+
+proc printBlockFile(s: string) =
+  whenColors:
+    case colorTheme
+    of "simple": stdout.styledWrite(styleBright, s)
+    of "bnw": stdout.styledWrite(styleUnderscore, s)
+    of "ack": stdout.styledWrite(styleUnderscore, fgGreen, s)
+    of "gnu": stdout.styledWrite(styleUnderscore, fgMagenta, s)
+
+proc printError(s: string) =
+  whenColors:
+    case colorTheme
+    of "simple", "bnw": stdout.styledWriteLine(styleBright, s)
+    of "ack", "gnu": stdout.styledWriteLine(styleReverse, fgRed, bgDefault, s)
+  stdout.flushFile()
+
+const alignment = 6
+
+proc printLineN(s: string, isMatch: bool) =
+  whenColors:
+    case colorTheme
+    of "simple": stdout.write(s)
+    of "bnw":
+      if isMatch: stdout.styledWrite(styleBright, s)
+      else: stdout.styledWrite(s)
+    of "ack":
+      if isMatch: stdout.styledWrite(fgYellow, s)
+      else: stdout.styledWrite(fgGreen, s)
+    of "gnu":
+      if isMatch: stdout.styledWrite(fgGreen, s)
+      else: stdout.styledWrite(fgCyan, s)
+
+proc printBlockLineN(s: string) =
+  whenColors:
+    case colorTheme
+    of "simple": stdout.styledWrite(styleBright, s)
+    of "bnw": stdout.styledWrite(styleUnderscore, styleBright, s)
+    of "ack": stdout.styledWrite(styleUnderscore, fgYellow, s)
+    of "gnu": stdout.styledWrite(styleUnderscore, fgGreen, s)
+
+type
+  SearchInfo = tuple[buf: string, filename: string]
+  MatchInfo = tuple[first: int, last: int;
+                    lineBeg: int, lineEnd: int, match: string]
+
+proc writeColored(s: string) =
+  whenColors:
+    case colorTheme
+    of "simple": terminal.writeStyled(s, {styleUnderscore, styleBright})
+    of "bnw": stdout.styledWrite(styleReverse, s)
+    # Try styleReverse & bgDefault as a work-around against nasty feature
+    # "Background color erase" (sticky background after line wraps):
+    of "ack": stdout.styledWrite(styleReverse, fgYellow, bgDefault, s)
+    of "gnu": stdout.styledWrite(fgRed, s)
+
+proc writeArrow(s: string) =
+  whenColors:
+    stdout.styledWrite(styleReverse, s)
+
+proc blockHeader(filename: string, line: int|string, replMode=false) =
+  if replMode:
+    writeArrow("     ->\n")
+  elif newLine:
+    if oneline:
+      printBlockFile(filename)
+      printBlockLineN(":" & $line & ":")
+    else:
+      printBlockLineN($line.`$`.align(alignment) & ":")
+    stdout.write("\n")
+
+proc lineHeader(filename: string, line: int|string, isMatch: bool) =
+  let lineSym =
+    if isMatch: $line & ":"
+    else: $line & " "
+  if not newLine:
+    if oneline:
+      printFile(filename)
+      printLineN(":" & lineSym, isMatch)
+    else:
+      printLineN(lineSym.align(alignment+1), isMatch)
+    stdout.write(" ")
+
+proc printMatch(fileName: string, mi: MatchInfo) =
+  let lines = mi.match.splitLines()
+  for i, l in lines:
+    if i > 0:
+      lineHeader(filename, mi.lineBeg + i, isMatch = true)
+    writeColored(l)
+    if i < lines.len - 1:
+      stdout.write("\n")
+
+proc printLinesBefore(si: SearchInfo, curMi: MatchInfo, nLines: int,
+                      replMode=false) =
+  # start block: print 'linesBefore' lines before current match `curMi`
+  let first = beforePattern(si.buf, curMi.first-1, nLines)
+  let lines = splitLines(substr(si.buf, first, curMi.first-1))
+  let startLine = curMi.lineBeg - lines.len + 1
+  blockHeader(si.filename, curMi.lineBeg, replMode=replMode)
+  for i, l in lines:
+    lineHeader(si.filename, startLine + i, isMatch = (i == lines.len - 1))
+    stdout.write(l)
+    if i < lines.len - 1:
+      stdout.write("\n")
+
+proc printLinesAfter(si: SearchInfo, mi: MatchInfo, nLines: int) =
+  # finish block: print 'linesAfter' lines after match `mi`
+  let s = si.buf
+  let last = afterPattern(s, mi.last+1, nLines)
+  let lines = splitLines(substr(s, mi.last+1, last))
+  if lines.len == 0: # EOF
+    stdout.write("\n")
   else:
-    stdout.write(line.`$`.align(alignment), ": ")
-  var x = beforePattern(s, t.first)
-  var y = afterPattern(s, t.last)
-  for i in x .. t.first-1: stdout.write(s[i])
-  writeColored(match)
-  for i in t.last+1 .. y: stdout.write(s[i])
-  stdout.write("\n")
+    stdout.write(lines[0]) # complete the line after match itself
+    stdout.write("\n")
+    let skipLine =  # workaround posix line ending at the end of file
+      if last == s.len-1 and s.len >= 2 and s[^1] == '\l' and s[^2] != '\c': 1
+      else: 0
+    for i in 1 ..< lines.len - skipLine:
+      lineHeader(si.filename, mi.lineEnd + i, isMatch = false)
+      stdout.write(lines[i])
+      stdout.write("\n")
+  if linesAfter + linesBefore >= 2 and not newLine: stdout.write("\n")
+
+proc printBetweenMatches(si: SearchInfo, prevMi: MatchInfo, curMi: MatchInfo) =
+  # continue block: print between `prevMi` and `curMi`
+  let lines = si.buf.substr(prevMi.last+1, curMi.first-1).splitLines()
+  stdout.write(lines[0]) # finish the line of previous Match
+  if lines.len > 1:
+    stdout.write("\n")
+    for i in 1 ..< lines.len:
+      lineHeader(si.filename, prevMi.lineEnd + i,
+                 isMatch = (i == lines.len - 1))
+      stdout.write(lines[i])
+      if i < lines.len - 1:
+        stdout.write("\n")
+
+proc printContextBetween(si: SearchInfo, prevMi, curMi: MatchInfo) =
+  # print context after previous match prevMi and before current match curMi
+  let nLinesBetween = curMi.lineBeg - prevMi.lineEnd
+  if nLinesBetween <= linesAfter + linesBefore + 1: # print as 1 block
+    printBetweenMatches(si, prevMi, curMi)
+  else: # finalize previous block and then print next block
+    printLinesAfter(si, prevMi, 1+linesAfter)
+    printLinesBefore(si, curMi, linesBefore+1)
+
+proc printReplacement(si: SearchInfo, mi: MatchInfo, repl: string,
+                      showRepl: bool, curPos: int,
+                      newBuf: string, curLine: int) =
+  printLinesBefore(si, mi, linesBefore+1)
+  printMatch(si.fileName, mi)
+  printLinesAfter(si, mi, 1+linesAfter)
   stdout.flushFile()
   if showRepl:
-    stdout.write(spaces(alignment-1), "-> ")
-    for i in x .. t.first-1: stdout.write(s[i])
-    writeColored(repl)
-    for i in t.last+1 .. y: stdout.write(s[i])
-    stdout.write("\n")
+    let newSi: SearchInfo = (buf: newBuf, filename: si.filename)
+    let miForNewBuf: MatchInfo =
+      (first: newBuf.len, last: newBuf.len,
+       lineBeg: curLine, lineEnd: curLine, match: "")
+    printLinesBefore(newSi, miForNewBuf, linesBefore+1, replMode=true)
+
+    let replLines = countLineBreaks(repl, 0, repl.len-1)
+    let miFixLines: MatchInfo =
+      (first: mi.first, last: mi.last,
+       lineBeg: curLine, lineEnd: curLine + replLines, match: repl)
+    printMatch(si.fileName, miFixLines)
+    printLinesAfter(si, miFixLines, 1+linesAfter)
     stdout.flushFile()
 
-proc processFile(pattern; filename: string; counter: var int) =
+proc doReplace(si: SearchInfo, mi: MatchInfo, i: int, r: string;
+               newBuf: var string, curLine: var int, reallyReplace: var bool) =
+  newBuf.add(si.buf.substr(i, mi.first-1))
+  inc(curLine, countLineBreaks(si.buf, i, mi.first-1))
+  if optConfirm in options:
+    printReplacement(si, mi, r, showRepl=true, i, newBuf, curLine)
+    case confirm()
+    of ceAbort: quit(0)
+    of ceYes: reallyReplace = true
+    of ceAll:
+      reallyReplace = true
+      options.excl(optConfirm)
+    of ceNo:
+      reallyReplace = false
+    of ceNone:
+      reallyReplace = false
+      options.excl(optConfirm)
+  else:
+    printReplacement(si, mi, r, showRepl=reallyReplace, i, newBuf, curLine)
+  if reallyReplace:
+    newBuf.add(r)
+    inc(curLine, countLineBreaks(r, 0, r.len-1))
+  else:
+    newBuf.add(mi.match)
+    inc(curLine, countLineBreaks(mi.match, 0, mi.match.len-1))
+
+proc processFile(pattern; filename: string; counter: var int, errors: var int) =
   var filenameShown = false
   template beforeHighlight =
     if not filenameShown and optVerbose notin options and not oneline:
-      stdout.writeLine(filename)
+      printBlockFile(filename)
+      stdout.write("\n")
       stdout.flushFile()
       filenameShown = true
 
@@ -146,59 +370,58 @@ proc processFile(pattern; filename: string; counter: var int) =
     try:
       buffer = system.readFile(filename)
     except IOError:
-      echo "cannot open file: ", filename
+      printError "Error: cannot open file: " & filename
+      inc(errors)
       return
   if optVerbose in options:
-    stdout.writeLine(filename)
+    printFile(filename)
+    stdout.write("\n")
     stdout.flushFile()
   var result: string
 
   if optReplace in options:
     result = newStringOfCap(buffer.len)
 
-  var line = 1
+  var lineRepl = 1
+  let si: SearchInfo = (buf: buffer, filename: filename)
+  var prevMi, curMi: MatchInfo
+  curMi.lineEnd = 1
   var i = 0
   var matches: array[0..re.MaxSubpatterns-1, string]
   for j in 0..high(matches): matches[j] = ""
   var reallyReplace = true
   while i < buffer.len:
     let t = findBounds(buffer, pattern, matches, i)
-    if t.first < 0 or t.last < t.first: break
-    inc(line, countLines(buffer, i, t.first-1))
-
-    var wholeMatch = buffer.substr(t.first, t.last)
+    if t.first < 0 or t.last < t.first:
+      if optReplace notin options and prevMi.lineBeg != 0: # finalize last match
+        printLinesAfter(si, prevMi, 1+linesAfter)
+        stdout.flushFile()
+      break
 
+    let lineBeg = curMi.lineEnd + countLineBreaks(buffer, i, t.first-1)
+    curMi = (first: t.first,
+             last: t.last,
+             lineBeg: lineBeg,
+             lineEnd: lineBeg + countLineBreaks(buffer, t.first, t.last),
+             match: buffer.substr(t.first, t.last))
     beforeHighlight()
     inc counter
     if optReplace notin options:
-      highlight(buffer, wholeMatch, "", t, filename, line, showRepl=false)
-    else:
-      let r = replace(wholeMatch, pattern, replacement % matches)
-      if optConfirm in options:
-        highlight(buffer, wholeMatch, r, t, filename, line, showRepl=true)
-        case confirm()
-        of ceAbort: quit(0)
-        of ceYes: reallyReplace = true
-        of ceAll:
-          reallyReplace = true
-          options.excl(optConfirm)
-        of ceNo:
-          reallyReplace = false
-        of ceNone:
-          reallyReplace = false
-          options.excl(optConfirm)
-      else:
-        highlight(buffer, wholeMatch, r, t, filename, line, showRepl=reallyReplace)
-      if reallyReplace:
-        result.add(buffer.substr(i, t.first-1))
-        result.add(r)
+      if prevMi.lineBeg == 0: # no previous match, so no previous block to finalize
+        printLinesBefore(si, curMi, linesBefore+1)
       else:
-        result.add(buffer.substr(i, t.last))
+        printContextBetween(si, prevMi, curMi)
+      printMatch(si.fileName, curMi)
+      stdout.flushFile()
+    else:
+      let r = replace(curMi.match, pattern, replacement % matches)
+      doReplace(si, curMi, i, r, result, lineRepl, reallyReplace)
 
-    inc(line, countLines(buffer, t.first, t.last))
     i = t.last+1
+    prevMi = curMi
+
   if optReplace in options:
-    result.add(substr(buffer, i))
+    result.add(substr(buffer, i))  # finalize new buffer after last match
     var f: File
     if open(f, filename, fmWrite):
       f.write(result)
@@ -206,10 +429,34 @@ proc processFile(pattern; filename: string; counter: var int) =
     else:
       quit "cannot open file for overwriting: " & filename
 
-proc hasRightExt(filename: string, exts: seq[string]): bool =
-  var y = splitFile(filename).ext.substr(1) # skip leading '.'
-  for x in items(exts):
-    if os.cmpPaths(x, y) == 0: return true
+proc hasRightFileName(path: string): bool =
+  let filename = path.lastPathPart
+  let ex = filename.splitFile.ext.substr(1) # skip leading '.'
+  if extensions.len != 0:
+    var matched = false
+    for x in items(extensions):
+      if os.cmpPaths(x, ex) == 0:
+        matched = true
+        break
+    if not matched: return false
+  for x in items(skipExtensions):
+    if os.cmpPaths(x, ex) == 0: return false
+  if includeFile.len != 0:
+    var matched = false
+    for x in items(includeFile):
+      if filename.match(x):
+        matched = true
+        break
+    if not matched: return false
+  for x in items(excludeFile):
+    if filename.match(x): return false
+  result = true
+
+proc hasRightDirectory(path: string): bool =
+  let dirname = path.lastPathPart
+  for x in items(excludeDir):
+    if dirname.match(x): return false
+  result = true
 
 proc styleInsensitive(s: string): string =
   template addx =
@@ -245,17 +492,32 @@ proc styleInsensitive(s: string): string =
         addx()
     else: addx()
 
-proc walker(pattern; dir: string; counter: var int) =
-  for kind, path in walkDir(dir):
-    case kind
-    of pcFile:
-      if extensions.len == 0 or path.hasRightExt(extensions):
-        processFile(pattern, path, counter)
-    of pcDir:
-      if optRecursive in options:
-        walker(pattern, path, counter)
-    else: discard
-  if existsFile(dir): processFile(pattern, dir, counter)
+proc walker(pattern; dir: string; counter: var int, errors: var int) =
+  if existsDir(dir):
+    for kind, path in walkDir(dir):
+      case kind
+      of pcFile:
+        if path.hasRightFileName:
+          processFile(pattern, path, counter, errors)
+      of pcLinkToFile:
+        if optFollow in options and path.hasRightFileName:
+          processFile(pattern, path, counter, errors)
+      of pcDir:
+        if optRecursive in options and path.hasRightDirectory:
+          walker(pattern, path, counter, errors)
+      of pcLinkToDir:
+        if optFollow in options and optRecursive in options and
+           path.hasRightDirectory:
+          walker(pattern, path, counter, errors)
+  elif existsFile(dir):
+    processFile(pattern, dir, counter, errors)
+  else:
+    printError "Error: no such file or directory: " & dir
+    inc(errors)
+
+proc reportError(msg: string) =
+  printError "Error: " & msg
+  quit "Run nimgrep --help for the list of options"
 
 proc writeHelp() =
   stdout.write(Usage)
@@ -275,7 +537,6 @@ when defined(posix):
   useWriteStyled = terminal.isatty(stdout)
   # that should be before option processing to allow override of useWriteStyled
 
-oneline = true
 for kind, key, val in getopt():
   case kind
   of cmdArgument:
@@ -290,7 +551,7 @@ for kind, key, val in getopt():
   of cmdLongOption, cmdShortOption:
     case normalize(key)
     of "find", "f": incl(options, optFind)
-    of "replace", "r": incl(options, optReplace)
+    of "replace", "!": incl(options, optReplace)
     of "peg":
       excl(options, optRegex)
       incl(options, optPeg)
@@ -301,27 +562,55 @@ for kind, key, val in getopt():
       incl(options, optRex)
       incl(options, optRegex)
       excl(options, optPeg)
-    of "recursive": incl(options, optRecursive)
+    of "recursive", "r": incl(options, optRecursive)
+    of "follow": incl(options, optFollow)
     of "confirm": incl(options, optConfirm)
     of "stdin": incl(options, optStdin)
     of "word", "w": incl(options, optWord)
     of "ignorecase", "i": incl(options, optIgnoreCase)
     of "ignorestyle", "y": incl(options, optIgnoreStyle)
     of "ext": extensions.add val.split('|')
+    of "noext": skipExtensions.add val.split('|')
+    of "excludedir", "exclude-dir": excludeDir.add rex(val)
+    of "includefile", "include-file": includeFile.add rex(val)
+    of "excludefile", "exclude-file": excludeFile.add rex(val)
     of "nocolor": useWriteStyled = false
     of "color":
       case val
       of "auto": discard
       of "never", "false": useWriteStyled = false
       of "", "always", "true": useWriteStyled = true
-      else: writeHelp()
+      else: reportError("invalid value '" & val & "' for --color")
+    of "colortheme":
+      colortheme = normalize(val)
+      if colortheme notin ["simple", "bnw", "ack", "gnu"]:
+        reportError("unknown colortheme '" & val & "'")
+    of "beforecontext", "before-context", "b":
+      try:
+        linesBefore = parseInt(val)
+      except ValueError:
+        reportError("option " & key & " requires an integer but '" &
+                    val & "' was given")
+    of "aftercontext", "after-context", "a":
+      try:
+        linesAfter = parseInt(val)
+      except ValueError:
+        reportError("option " & key & " requires an integer but '" &
+                    val & "' was given")
+    of "context", "c":
+      try:
+        linesContext = parseInt(val)
+      except ValueError:
+        reportError("option --context requires an integer but '" &
+                    val & "' was given")
+    of "newline", "l": newLine = true
     of "oneline": oneline = true
-    of "group": oneline = false
+    of "group", "g": oneline = false
     of "verbose": incl(options, optVerbose)
     of "filenames": incl(options, optFilenames)
     of "help", "h": writeHelp()
     of "version", "v": writeVersion()
-    else: writeHelp()
+    else: reportError("unrecognized option '" & key & "'")
   of cmdEnd: assert(false) # cannot happen
 
 checkOptions({optFind, optReplace}, "find", "replace")
@@ -329,6 +618,9 @@ checkOptions({optPeg, optRegex}, "peg", "re")
 checkOptions({optIgnoreCase, optIgnoreStyle}, "ignore_case", "ignore_style")
 checkOptions({optFilenames, optReplace}, "filenames", "replace")
 
+linesBefore = max(linesBefore, linesContext)
+linesAfter  = max(linesAfter,  linesContext)
+
 if optStdin in options:
   pattern = ask("pattern [ENTER to exit]: ")
   if pattern.len == 0: quit(0)
@@ -336,9 +628,10 @@ if optStdin in options:
     replacement = ask("replacement [supports $1, $# notations]: ")
 
 if pattern.len == 0:
-  writeHelp()
+  reportError("empty pattern was given")
 else:
   var counter = 0
+  var errors = 0
   if filenames.len == 0:
     filenames.add(os.getCurrentDir())
   if optRegex notin options:
@@ -350,7 +643,7 @@ else:
       pattern = "\\i " & pattern
     let pegp = peg(pattern)
     for f in items(filenames):
-      walker(pegp, f, counter)
+      walker(pegp, f, counter, errors)
   else:
     var reflags = {reStudy}
     if optIgnoreStyle in options:
@@ -362,5 +655,9 @@ else:
     let rep = if optRex in options: rex(pattern, reflags)
               else: re(pattern, reflags)
     for f in items(filenames):
-      walker(rep, f, counter)
+      walker(rep, f, counter, errors)
+  if errors != 0:
+    printError $errors & " errors"
   stdout.write($counter & " matches\n")
+  if errors != 0:
+    quit(1)