KSH脚本求助：读取文件输入写入CSV同一行时输出错位问题

Hey Jay, let's break down why your script is causing misaligned output and get it sorted so you can produce clean, single-line CSV entries in the FROM:,TO: format you want.

Common Issues with Your Original Approach #

Chances are your script looks something like this (a typical misstep with for loops and grep):

for entry in $(cat your_input_file.txt); do
  grep "FROM:" <<< "$entry"
  grep "TO:" <<< "$entry"
done > output.csv

Here's what's going wrong:

• The for entry in $(cat ...) syntax splits your input by whitespace (not lines), so lines with spaces get broken into multiple loop iterations.
• Each grep command outputs its result on a new line, so your FROM: and TO: values end up on separate rows instead of the same CSV line.

Solution 1: Process Lines with while read (for line-by-line input) #

If each line in your input file contains both a FROM: and TO: value, use a while read loop to capture each full line, extract both values, and print them together in one CSV row:

#!/bin/bash
# Optional: Add a CSV header
echo "FROM,TO"

# Read each line of the input file
while IFS= read -r line; do
  # Extract FROM value (remove "FROM:" and trim extra spaces)
  from=$(echo "$line" | grep -oP 'FROM:\s*\K.*')
  # Extract TO value (remove "TO:" and trim extra spaces)
  to=$(echo "$line" | grep -oP 'TO:\s*\K.*')
  # Print both values on the same CSV line
  printf "%s,%s\n" "$from" "$to"
done < your_input_file.txt > output.csv

Solution 2: Group Multi-line Entries with awk #

If your input has FROM: and TO: on separate lines (like the sample below), use awk to pair them up and output single CSV rows:

Sample input:

FROM: alice@example.com
TO: bob@example.com
FROM: charlie@example.com
TO: dave@example.com

Here's the awk script to handle this:

awk '
  # Capture FROM value when we hit a FROM line
  /FROM:/ { from = substr($0, 6) }  # Skip "FROM:" (first 5 characters)
  # When we hit a TO line, print the paired FROM/TO as CSV
  /TO:/ { 
    to = substr($0, 4)  # Skip "TO:" (first 3 characters)
    printf "%s,%s\n", from, to 
  }
' your_input_file.txt > output.csv

Key Notes #

• Use printf instead of echo for consistent output (avoids issues with special characters).
• If your values might contain commas, wrap them in double quotes like this: printf "\"%s\",\"%s\"\n" "$from" "$to" to comply with CSV standards.

内容的提问来源于stack exchange，提问作者jay