bash:根据列的一部分拆分CSV檔案

如何：

awk -F', ' '
  { date = substr($2,1,10) }
  !(date in outfile) { outfile[date] = "file_" (++numout) ".csv" }
  { print > outfile[date] }
' file.csv

如果檔案很大且具有许多唯一的日期，則可能需要使用以下方法来防止"打開的檔案過多"錯誤：

 { print >> outfile[date]; close(outfile[date]) }

$ cat tst.sh
#!/usr/bin/env bash
awk -F'[ -]' -v OFS='\t' '{print $2$3, NR, $0}' "${@:--}" |
sort -k1,1n -k2,2n |
cut -f3- |
awk -F'[ -]' '
    { curr = $2$3 }
    curr != prev {
        close(out)
        out = "file_" (++cnt) ".csv"
        prev = curr
    }
    { print > out }
'

./tst.sh file

$ head file_*
==> file_1.csv <==
id1, 2017-04-28T19:59:00, 80
id2, 2017-04-28T03:14:35, e4
id5, 2017-04-28T00:31:54, 65
id7, 2017-04-28T21:04:30, 7f
==> file_2.csv <==
id0, 2020-12-12T07:18:26, 7f
id3, 2020-12-12T23:45:09, ff
id4, 2020-12-12T09:12:34, a1
id6, 2020-12-12T20:13:47, 45

以上內容可与任何POSIX awk，排序和剪切一起稳健，高效且可移植地工作，並將輸入順序保留在輸出檔案中。

這是前三步重新排列輸入檔案內容的方式：

$ cat file
id0, 2020-12-12T07:18:26, 7f
id1, 2017-04-28T19:59:00, 80
id2, 2017-04-28T03:14:35, e4
id3, 2020-12-12T23:45:09, ff
id4, 2020-12-12T09:12:34, a1
id5, 2017-04-28T00:31:54, 65
id6, 2020-12-12T20:13:47, 45
id7, 2017-04-28T21:04:30, 7f

因此，在最终的awk指令碼執行時，它按年+月从$ 2開始按行排序，並保留所有具有相同日期和時間的行的輸入順序：

$ awk -F'[ -]' -v OFS='\t' '{print $2$3, NR, $0}' file
202012  1       id0, 2020-12-12T07:18:26, 7f
201704  2       id1, 2017-04-28T19:59:00, 80
201704  3       id2, 2017-04-28T03:14:35, e4
202012  4       id3, 2020-12-12T23:45:09, ff
202012  5       id4, 2020-12-12T09:12:34, a1
201704  6       id5, 2017-04-28T00:31:54, 65
202012  7       id6, 2020-12-12T20:13:47, 45
201704  8       id7, 2017-04-28T21:04:30, 7f

$ awk -F'[ -]' -v OFS='\t' '{print $2$3, NR, $0}' file | sort -k1,1n -k2,2n
201704  2       id1, 2017-04-28T19:59:00, 80
201704  3       id2, 2017-04-28T03:14:35, e4
201704  6       id5, 2017-04-28T00:31:54, 65
201704  8       id7, 2017-04-28T21:04:30, 7f
202012  1       id0, 2020-12-12T07:18:26, 7f
202012  4       id3, 2020-12-12T23:45:09, ff
202012  5       id4, 2020-12-12T09:12:34, a1
202012  7       id6, 2020-12-12T20:13:47, 45

$ awk -F'[ -]' -v OFS='\t' '{print $2$3, NR, $0}' file | sort -k1,1n -k2,2n | cut -f3-
id1, 2017-04-28T19:59:00, 80
id2, 2017-04-28T03:14:35, e4
id5, 2017-04-28T00:31:54, 65
id7, 2017-04-28T21:04:30, 7f
id0, 2020-12-12T07:18:26, 7f
id3, 2020-12-12T23:45:09, ff
id4, 2020-12-12T09:12:34, a1
id6, 2020-12-12T20:13:47, 45

按原樣行事，意味着先做 sort 然後分成不同的檔案，也避免使用 awk 陣列：

<infile sort -t, -k2 \
|awk -F, '{
     substr($2,1,10)!=prev && nxt++;
     print >>("file_"nxt".csv"); close("file_"nxt".csv");
     prev=substr($2,1,10);
}'