【问题标题】：Add double quotes to the first line of a csv file via command line通过命令行将双引号添加到 csv 文件的第一行
【发布时间】：2019-10-05 11:16:17
【问题描述】：

我有这个 csv 文件，我注意到在导出过程中没有添加起始报价。实际上在 ubuntu 中，如果我输入：

head -n 1 file.csv

我得到这个输出：

801","40116","Hazelnut MT -L","Thursday Promo","Large","","5.9000","","801","1.0000","","3.6500","2.2500",".0000","default","","","","","Chatime","02/06/2014","09125a9cfffd4143a00e73e3b62f15f2","CB01","",".0000","5.9000","6.9000",".0000",".0000",".0000",".0000",".0000",".0000","0","","0","0","0","","","","","","","","","Modern Milk Tea","","","0","","","1","0","","","","","","","","0","Hau Chan","","","","","","","","","","0","","","","","","","-1","","","","","","","","","","","","0","00000000420714AA","2014-06-02","1900-01-01","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""

是否有一些命令类型可以帮助我添加缺少的起始引号？

【问题讨论】：

有，但您也可以在文本编辑器中打开文件并手动添加报价。
这是一个 70gb 的 csv 文件。我想我无法打开它。
哦，好吧……这改变了一切。
只是为了确定：引号是仅在第一行中丢失还是在每一行中都丢失了？就像 oguz ismail 我假设它只在第一行中丢失，因为您只显示了那一行。
@Socowi 仅在第一行。接下来是正确的引号。

标签： regex bash shell command-line

【解决方案1】：

这应该适用于每个 posix-shell：

printf \" | cat - file.csv > repaired-file.csv

如果你对结果满意，你可以覆盖原来的

mv repaired-file.csv file.csv

由于您的文件有 70GB 大，您可能希望避免创建第二个文件，但这比看起来要难。当然，有诸如sed 的就地选项 (-i) 和来自moreutils 的sponge 实用程序之类的东西，但它们并不像您预期的那样就地工作。 sed -i 和 sponge 都使用临时文件或将整个文件保存在内存中（不再适用于 70GB）。可以在this blog post 中找到有关真正就地编辑的精彩研究。结论：没有标准工具支持真正的就地编辑。但是下面的perl 单行应该可以工作（已经适应了你的需要）。

perl <<'EOF'
  use Tie::File;
  my @a;
  tie @a, 'Tie::File', 'path/to/your/file' or die 'Cannot tie file';
  $a[0] = '"' . $a[0];
EOF

基准测试

出于兴趣，我运行了此处讨论的命令并测量了它们的运行时间。

9.3 GiB 输入文件f 是使用seq 1000000000 > f 生成的。在为单个命令计时之前，我总是重新生成f 并使用sync && echo 3 | sudo tee /proc/sys/vm/drop_caches 清空系统缓存。我的系统有足够的内存来保存整个文件，但我手动监控了内存使用情况——所有命令只使用了几 KB 的内存。

printf \" | cat - f > f2; mv f2 f 1m 05s
perl … # script from above 1m 32s
sed -i '1s/^/"/' f 25m 57s（也一直使用 100% CPU）

cat 命令比perl 脚本快，我自己也有点惊讶。但是，这是有道理的，因为 perl 脚本会进行大量搜索（可以使用 strace 看到），而 cat 只是复制。

总结：如果您有足够的磁盘空间，请使用cat 命令。如果文件大于系统上剩余的可用磁盘空间，则使用perl 脚本。

【讨论】：