gh-108095: Add re.grep module

Author: serhiy-storchaka

Lib/re/grep.py

@@ -0,0 +1,248 @@
+import sys
+import argparse
+import re
+from collections import deque
+
+
+def find(patterns, line):
+    for pat in patterns:
+        if pat.search(line) is not None:
+            return True
+    return False
+
+def findall(patterns, line):
+    if len(patterns) == 1:
+        for m in patterns[0].finditer(line):
+            yield m.group()
+        return
+
+    i = 0
+    while True:
+        begin = len(line) + 1
+        end = -1
+        best_span = (len(line) + 1, 1)
+        for pat in patterns:
+            m = pat.search(line, i)
+            if m is not None:
+                # Find the longest of the first matches.
+                best_span = min(best_span, (m.begin(), -m.end()))
+                if best_span == (i, -len(line)):
+                    # Matches the rest of line.
+                    break
+        begin = best_span[0]
+        end = -best_span[1]
+        if end < 0:
+            break
+        yield line[begin:end]
+        i = end
+        if begin == end:
+            i += 1
+
+def grep(opts, patterns, file, filename):
+    def print_line(sep, ln, line):
+        if opts.filename:
+            print(filename, end=sep)
+        if opts.line_number:
+            print(ln, end=sep)
+        print(line)
+
+    fast_exit = opts.quiet or opts.filename_only is not None
+    prev_lines = deque(maxlen=opts.before_context)
+    after_lines = 0
+    next_group = None
+    total_count = 0
+    found = False
+    for ln, line in enumerate(file, 1):
+        line = line.removesuffix('\n')
+        if opts.only_matching:
+            for match in findall(patterns, line):
+                print_line(':', ln, match)
+                found = True
+        else:
+            matches = find(patterns, line)
+            if opts.invert_match:
+                matches = not matches
+            if matches:
+                found = True
+                if fast_exit:
+                    break
+                elif opts.count:
+                    total_count += 1
+                else:
+                    if next_group and ln > next_group:
+                        print(opts.group_separator)
+                    for ln2, line2 in enumerate(prev_lines, ln - len(prev_lines)):
+                        print_line('-', ln2, line2)
+                    prev_lines.clear()
+                    print_line(':', ln, line)
+                    after_lines = opts.after_context
+                    next_group = (None if opts.group_separator is None else
+                                  ln + after_lines + opts.before_context + 1)
+            elif not (fast_exit or opts.count):
+                if after_lines:
+                    print_line('-', ln, line)
+                    after_lines -= 1
+                else:
+                    prev_lines.append(line)
+    if fast_exit:
+        if opts.filename_only == found:
+            print(filename)
+    elif opts.count:
+        if opts.filename:
+            print(filename, end=':')
+        print(total_count)
+    return found
+
+def read_from_file(filename):
+    with open(filename, encoding=sys.stdin.encoding,
+              errors=sys.stdin.errors) as f:
+        return [line.removesuffix('\n') for line in f.readlines()]
+
+def main():
+    parser = argparse.ArgumentParser(add_help=False)
+    # Add --help option explicitly to avoid conflict in the -h option.
+    parser.add_argument('--help',
+            action='help', default=argparse.SUPPRESS,
+            help='show this help message and exit')
+
+    parser.set_defaults(label='(standard input)', group_separator='--')
+
+    parser.add_argument('files',
+            nargs=argparse.REMAINDER,
+            metavar='FILES',
+            help='Files to search.')
+
+    grp = parser.add_argument_group('Matching Control')
+    grp.add_argument('-e', '--regexp',
+            action='append', dest='patterns',
+            metavar='PATTERN',
+            help='Use PATTERN as the pattern.')
+    grp.add_argument('-f', '--file',
+            action='extend', dest='patterns', type=read_from_file,
+            metavar='PATTERN_FILE',
+            help='Obtain patterns from PATTERN_FILE, one per line.')
+    grp.add_argument('-F', '--fixed-strings',
+            action='store_true',
+            help='Interpret patterns as fixed strings.')
+    grp.add_argument('-i', '--ignore-case',
+            action='store_true',
+            help='Ignore case distinctions in patterns and input data.')
+    grp.add_argument('--no-ignore-case',
+            action='store_false', dest='ignore_case',
+            help='Do not ignore case distinctions in patterns and input data.  '
+            'This is the default.')
+    grp.add_argument('-v', '--invert-match',
+            action='store_true',
+            help='Invert the sense of matching, to select non-matching lines.')
+    grp.add_argument('-w', '--word-regexp',
+            action='store_true',
+            help='Select only those lines containing matches that form whole words.')
+    grp.add_argument('-x', '--line-regexp',
+            action='store_true',
+            help='Select only those matches that exactly match the whole line.')
+
+    grp = parser.add_argument_group('Output Control')
+    grp.add_argument('-c', '--count',
+            action='store_true',
+            help='Suppress normal output; instead print a count of matching '
+            'lines for each input file.')
+    grp.add_argument('-L', '--files-without-match',
+            action='store_false', dest='filename_only', default=None,
+            help='Suppress normal output; instead print the name of each input '
+            'file from which no output would normally have been printed.')
+    grp.add_argument('-l', '--files-with-match',
+            action='store_true', dest='filename_only',
+            help='Suppress normal output; instead print the name of each input '
+            'file from which output would normally have been printed.')
+    grp.add_argument('-o', '--only-matching',
+            action='store_true',
+            help='Print only the matched (non-empty) parts of a matching line, '
+            'with each such part on a separate output line.')
+    grp.add_argument('-q', '--quiet',
+            action='store_true',
+            help='Quiet; do not write anything to standard output.  '
+            'Exit immediately with zero status if any match is found.')
+
+    grp = parser.add_argument_group('Output Line Prefix Control')
+    grp.add_argument('-H', '--with-filename',
+            action='store_true', dest='filename', default=None,
+            help='Print the file name for each match.  '
+            'This is the default when there is more than one file to search.')
+    grp.add_argument('-h', '--no-filename',
+            action='store_false', dest='filename',
+            help='Suppress the prefixing of file names on output.  '
+            'This is the default when there is only one file (or only standard '
+            'input) to search.')
+    grp.add_argument('-n', '--line-number',
+            action='store_true',
+            help='Prefix each line of output with the 1-based line number '
+            'within its input file.')
+
+    grp = parser.add_argument_group('Context Line Control')
+    grp.add_argument('-A', '--after-context',
+            type=int, metavar='NUM',
+            help='Print NUM lines of trailing context after matching lines.')
+    grp.add_argument('-B', '--before-context',
+            type=int, metavar='NUM',
+            help='Print NUM lines of leading context before matching lines.')
+    grp.add_argument('-C', '--context',
+            type=int, default=0, metavar='NUM',
+            help='Print NUM lines of output context.')
+
+    opts = parser.parse_args()
+
+    patterns = opts.patterns or []
+    if opts.fixed_strings:
+        patterns = [re.escape(pat) for pat in patterns]
+    if opts.line_regexp:
+        patterns = [fr'\A(?:{pat})\Z' for pat in patterns]
+    elif opts.word_regexp:
+        patterns = [fr'\b(?:{pat})\b' for pat in patterns]
+    flags = re.IGNORECASE if opts.ignore_case else 0
+    patterns = [re.compile(pat, flags) for pat in patterns]
+
+    # By default print filenames only if more than one file is specified.
+    if opts.filename is None:
+        opts.filename = len(opts.files) > 1
+    # -C sets -A and -B if they are not specified explicitly.
+    if opts.after_context is None:
+        opts.after_context = opts.context
+    if opts.before_context is None:
+        opts.before_context = opts.context
+    # -q, -l, -L and -c suppresses normal output.
+    if opts.quiet or opts.filename_only is not None or opts.count:
+        opts.only_matching = False
+        opts.after_context = opts.before_context = 0
+    # -vo suppresses normal output.
+    if opts.only_matching and opts.invert_match:
+        opts.only_matching = False
+        opts.quiet = True
+    # -o suppresses context output.
+    if opts.only_matching:
+        opts.after_context = opts.before_context = 0
+    # Only print group separator for non-zero context.
+    if not (opts.after_context or opts.before_context):
+        opts.group_separator = None
+
+    found = False
+    for filename in opts.files or ['-']:
+        if filename == '-':
+            found |= grep(opts, patterns, sys.stdin, opts.label)
+        else:
+            with open(filename, encoding=sys.stdin.encoding,
+                      errors=sys.stdin.errors) as f:
+                found |= grep(opts, patterns, f, filename)
+        if found and opts.quiet:
+            break
+    return found
+
+
+if __name__ == '__main__':
+    try:
+        found = main()
+    except SystemExit:
+        raise
+    except BaseException as e:
+        print(f'error: {e!r}')
+        sys.exit(2)
+    sys.exit(0 if found else 1)