Question

我的互联网连接很差，并尝试下载三次相同的rar存档（＆gt; 500 Mo）。每个文件都已损坏，但我希望可以创建三个已损坏的第四个文件的交集而没有任何损坏我对diff或comm不满意，不知道是否可以用它来做我想做的事谢谢你的帮助！

Answer 1

在评论中遵循chepner的想法，以下是我将如何重建可能的原文。

#!/bin/bash

FILE1="$1"
FILE2="$2"
FILE3="$3"
RESFILE="$4"

diff_at() {
  POS=$(cmp "$1" "$2" -i $3 | sed 's/,//' | cut -d ' ' -f 5)
  if [ "$POS" == "" ]; then
    POS=$(du -b "$1" "$2" | cut -f 1 | sort | head -n1) # min()
  fi
  echo $POS
}

max() {
  if [ $# -eq 0 ]; then # Degenerate case
    echo ""
  elif [ $# -eq 1 ]; then # Base case
    echo $(($1 + 0)) # Strings are interpreted as 0
  else
    V=$1
    shift
    M=$(max $@)
    echo $(($V > $M ? $V : $M))
  fi
}

# Shallow check of arguments
if [ $# -ne 4 ]; then
  echo "Provide three files to compare and a file to write output into."
  exit 1
fi

# If one of them is larger, you cannot compare its (probable) correctness
S1=$(du -b "$FILE1" | cut -f 1)
S2=$(du -b "$FILE2" | cut -f 1)
S3=$(du -b "$FILE3" | cut -f 1)
if [ $S1 -gt $S2 -a $S1 -gt $S3 -o $S2 -gt $S1 -a $S2 -gt $S3 -o $S3 -gt $S2 -a $S3 -gt $S1 ]; then
  echo "$0: Unable to reconstruct original file."
  exit 1
fi
FILESIZE=$(max $S1 $S2 $S3)

# The idea is that of extracting and appending the common part
truncate -s 0 "$RESFILE" # This will overwrite existing output
BIAS=0
while [ $BIAS -lt $FILESIZE ]; do
  I12=$(diff_at "$FILE1" "$FILE2" $BIAS)
  I23=$(diff_at "$FILE2" "$FILE3" $BIAS)
  I31=$(diff_at "$FILE3" "$FILE1" $BIAS)

  # Unreconstructible, aka all of them differ at the same byte
  if [ $I12 -eq $I23 -a $I12 -eq $I31 ]; then
    echo "$0: Unable to reconstruct original file."
    break;
  fi

  # Biggest common part
  MAXBYTE=$(max $I12 $I23 $I31)

  # Exclude the file with wrong byte
  if [ $I12 -eq $MAXBYTE -o $I31 -eq $MAXBYTE ]; then
    tail -c+$(($BIAS + 1)) "$FILE1" | head -c $(($MAXBYTE - 1)) >> "$RESFILE"
  else
    tail -c+$(($BIAS + 1)) "$FILE2" | head -c $(($MAXBYTE - 1)) >> "$RESFILE"
  fi

  # Update position
  BIAS=$(($BIAS + $MAXBYTE - 1))
done

为了处理＆＃34;猜测＆＃34; （在同一位置的所有三个字节都不同的情况下），您需要提交对脚本的更改。

我认为从许多角度来看，有比上面更好的选择，所以请将其视为快速和肮脏的。

三个文件的交叉

1 个答案: