Replace First Few Lines with First Few Lines from Other File

Replace first few lines with first few lines from other file

awk is your friend

Script

# awk 'NR==FNR && FNR<=3 || NR>FNR && FNR>4' file2 file1

Output

1a
2a
3a
5
6
7
8
9
10

Tips

• NR - Total number of records processed
• FNR - Total number of records processed but resets when reading a new file.
• When a condition evaluates to true and no extra commands are given,awk just prints.
  
  

  ---

All good :-)

how to replace the first line of a file with the first line of another file

This might work for you (GNU sed):

sed -e '1R file1' -e '1d' file2

Read the first line of file2. Read the first line of file1 and insert it into the output, then delete the first line of file2. Now read and output the rest of file2.

replace a string from first line on multiple files

You are very close with your code, but you need to account for the trailing / char after the . char.

Assuming you are using a modern sed with the -i (inplace-edit) option you can do

sed -i '1s@supersonic\./@supersonic.com/@' * 

Note that rather than have to escape / inside of the s/srchpat\/withSlash/replaceStr/', you can use another char after the the s command as the delimiter, here I use s@...@...@. If your search pattern had a @ char, then you would have to use a different char.

Some older versions of sed need to you to escape the alternate delimiter at the first use, so

     sed 's\@srchStr@ReplStr@' file 

for those cases.

If you're using a sed that doesn't support the -i options, then
you'll need to loop on your file, and manage the tmp files, i.e.

 for f in *.html ; do
    sed '1s@supersonic\./@supersonic.com/@' "$f" > /tmp/"$f".fix \
    && /bin/mv /tmp/"$f".fix "$f"
 done

Warning

But as you're talking about 10,000+files, you'll want to do some testing before using either of these solutions. Copy a good random set of those files to /tmp/mySedTest/ dir and run one of these solutions there to make sure there are no surprises.

And you're likely to blow out the cmd-line MAX_SIZE with 10,000+ files, so read about find and xargs. There are many posts here about [sed] find xargs. Check them out if needed.

IHTH

Replace next N lines before a first/second/third/... match including the match

Here's a BSD sed version (comment.sed):

/Text/, /}/ {
    s|^|//|
    /}/ {
        :idle
        n
        b idle
    }
}

The first line /Text/, /}/ is a regex address range. Every line within that that range (inclusive) will be commented out. At the end of this range, the second /}/, we loop back to the idle label consuming the rest of the file. Otherwise the address range would also comment out the second Text block.

A one line version:

sed '/Text/, /}/ {s|^|//|; /}/ {:idle; n; b idle}}' input

To test:

diff expect <(sed -f comment.sed input) && echo ok

Find line in file and replace it with line from another file

Your sed attempt contains several unexplained errors; it's actually hard to see what you are in fact trying to do.

You probably want to do something along the lines of

sed '3!d;s%.*%s/^matching\.string\.here.*/&/%' file2 |
sed -f - -i file1

It's unclear what you hope for the /s to mean; does your sed have a flag with this name?

This creates a sed script from the third line of file2; take out the pipeline to sed -f - to see what the generated script looks like. (If your sed does not allow you to pass in a script on standard input, you will have to write it to a temporary file, and then pass that to the second sed.)

Anyway, this is probably both simpler and more robust using Awk.

awk 'NR==3 && NR==FNR { keep=$0; next }
    /^matching\.string\.here/ { $0 = keep } 1' file2 file1

This writes the new content to standard output. If you have GNU Awk, you can explore its -i inplace option; otherwise, you will need to write the result to a file, then move it back to file1.

how to replace first line of a file using python or other tools?

Using Python 3:

import argparse

from sys import exit

from os.path import getsize

# collect command line arguments
parser = argparse.ArgumentParser()
parser.add_argument('-p', '--parameter', required=True, type=str)
parser.add_argument('-f', '--file', required=True, type=str)
args = parser.parse_args()

# check if file is empty
if getsize(args.file) == 0:
    print('Error: %s is empty' % args.file)
    exit(1)

# collect all lines first
lines = []
with open(args.file) as file:
    first_line = next(file)

    # Check if '=' sign exists in first line
    if '=' not in first_line:
        print('Error: first line is invalid')
        exit(1)

    # split first line and append new line
    root, parameter = first_line.split('=')
    lines.append('%s=%s\n' % (root, args.parameter))

    # append rest of lines normally
    for line in file:
        lines.append(line)

# rewrite new lines back to file
with open(args.file, 'w') as out:
    for line in lines:
        out.write(line)

Which works as follows:

$ cat hanlp.properties
root=/Users/pan/Documents
other content
$ python3 script.py --file hanlp.properties --parameter /Users/a/b
$ cat hanlp.properties
root=/User/a/b
other content

---

Related Topics