1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
#!/usr/bin/env python3
# Copyright (c) 2020 Cisco and/or its affiliates.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""A script simplifying replacement of blocks of lines.
A bash solution created by combining these two:
https://unix.stackexchange.com/a/181215
https://stackoverflow.com/a/23849180
does not seem to work if the blocks contain complicated characters.
"""
import argparse
import os
import tempfile
def main():
"""Main function for the block replacing script."""
description = '''Replace a block of lines with another block.
Both block-to-replace and replacing-block are read from a file.
The replacement is performed on a file, in-place.
Only first block occurence is replaced.
If the block-to-replace is preceded by a partial match,
it may not be recognized.
The current implementation uses temporary files,
created in the working directory.
if something fails, thise temporary files need to be deleted manually.
TODO: Preserve target attributes. Maybe https://pypi.org/project/in-place/
'''
parser = argparse.ArgumentParser(description)
parser.add_argument(
u"before", type=str,
help=u"Path to file containing the old content to replace."
)
parser.add_argument(
u"after", type=str,
help=u"Path to file containing the new content to replace with."
)
parser.add_argument(
u"targets", metavar=u"target", nargs=u"+", type=str,
help=u"Paths to file where the replacement should be made."
)
args = parser.parse_args()
do_it(args)
def do_it(args):
"""Read contents, create edited target, replace the original target with it.
:param args: Parsed command line arguments.
:type args: Object (typically argparse.Namespace) which contains
"before", "after" and "target" fields.
"""
with open(args.before, u"r") as file_in:
content_before = file_in.readlines()
before_len = len(content_before)
with open(args.after, u"r") as file_in:
content_after = file_in.readlines()
for target in args.targets:
with tempfile.NamedTemporaryFile(
dir=u".", mode=u"w", delete=False
) as file_out:
with open(target, u"r") as file_in:
# Phase one, searching for content, copying what does not match.
buffer_lines = list()
line_index_to_check = 0
content_found = False
while 1:
line_in = file_in.readline()
if not line_in:
print(f"{target}: Content not found.")
for line_out in buffer_lines:
file_out.write(line_out)
buffer_lines = list()
break
if line_in != content_before[line_index_to_check]:
line_index_to_check = 0
if buffer_lines:
for line_out in buffer_lines:
file_out.write(line_out)
buffer_lines = list()
file_out.write(line_in)
continue
buffer_lines.append(line_in)
line_index_to_check += 1
if line_index_to_check < before_len:
continue
# Buffer has the match! Do not write it.
content_found = True
break
if not content_found:
file_out.close()
os.remove(file_out.name)
continue
# Phase two, write the replacement instead.
for line_out in content_after:
file_out.write(line_out)
# Phase three, copy the rest of the file.
while 1:
line_in = file_in.readline()
if not line_in:
print(f"{target}: Replacement done.")
break
file_out.write(line_in)
os.replace(file_out.name, target)
if __name__ == u"__main__":
main()
|
