在Bash中将单行文本中每第3个逗号替换为换行符

Got it, let's fix this single-line CSV by splitting it into proper rows every 3 fields (replacing every 3rd comma with a newline). Here are a few reliable methods using common tools:

Using sed (Unix/Linux/macOS) #

This uses extended regular expressions to match groups of 3 fields and replace the trailing comma with a newline:

sed -E 's/(([^,]+,){2}[^,]+),/\1\n/g' input.txt

• -E enables extended regex (avoids escaping parentheses on most systems)
• The regex (([^,]+,){2}[^,]+) captures a full set of 3 fields (e.g., Name,Age,Year)
• We replace the comma immediately after this group with a newline (\n), and apply this globally (g)

Using awk #

Awk makes it easy to loop through fields and print them in chunks:

awk -F, '{
    for(i=1; i<=NF; i++) {
        printf "%s", $i
        if (i % 3 == 0 && i < NF) printf "\n"
        else if (i < NF) printf ","
    }
    print ""
}' input.txt

• -F, sets the field separator to a comma
• We loop through each field, printing it followed by either a comma (for non-ending fields in a chunk) or a newline (after every 3rd field)
• The final print "" adds a trailing newline to the output

Using Python #

If you prefer a script-based approach, Python is straightforward:

# Read the input file
with open("input.txt", "r") as f:
    content = f.read().strip()

# Split into individual fields
fields = content.split(',')

# Print every 3 fields as a single line
for i in range(0, len(fields), 3):
    print(','.join(fields[i:i+3]))

• This reads the entire line, splits it into a list of fields, then joins every 3 fields back into a comma-separated line and prints it

Testing with your sample input #

Input line: Name,Age,Year,Michael,27,2018,Carl,19,2018
Output from any of the above methods:

Name,Age,Year
Michael,27,2018
Carl,19,2018

内容的提问来源于stack exchange，提问作者MJCS