awk - 如何在awk中抑制默认打印？

Question

这是使用 gawk 4.0.0，运行在带有 cygwin 的 Windows 7 上。该程序被调用如下

gawk -f procjournal.gawk testdata

我有一些看起来像这样的数据:

"Date";"Type";"Amount";"Balance"
"6/11/2013 11:51:17 AM";"Transaction Tax";-427.5;399313884.46
"6/11/2013 11:51:17 AM";"Market Transaction";47500;399314311.96
"6/11/2013 11:12:42 AM";"Transaction Tax";-549.92;399266811.96
"6/11/2013 11:12:42 AM";"Market Transaction";61101.78;399267361.88

我想提取交易行，从第一个字段中去除日期部分，并将时间戳重新格式化为小数。我想我可以用这个 awk 程序做到这一点:

FS=";"
OFS=";"
/Market Transaction/ {
    split($1, itemdate, " ");
    tmp = itemdate[2];
    split(tmp, hms, ":");
    timestamp = hms[3] + (hms[2] * 60) + (hms[1] * 3600);
    if (itemdate[3] == "AM")
       timestamp += 12 * 3600;
    timestamp /= 3600.0;
    $1 = timestamp;
    print;
}

但我的输出是这样的:

"Date";"Type";"Amount";"Balance"
"Date";"Type";"Amount";"Balance"
"6/11/2013 11:51:17 AM";"Transaction Tax";-427.5;399313884.46
"6/11/2013 11:51:17 AM";"Transaction Tax";-427.5;399313884.46
"6/11/2013 11:51:17 AM";"Market Transaction";47500;399314311.96
"6/11/2013 11:51:17 AM";"Market Transaction";47500;399314311.96
11.8547;"Market Transaction";47500;399314311.96
"6/11/2013 11:12:42 AM";"Transaction Tax";-549.92;399266811.96
"6/11/2013 11:12:42 AM";"Transaction Tax";-549.92;399266811.96
"6/11/2013 11:12:42 AM";"Market Transaction";61101.78;399267361.88
"6/11/2013 11:12:42 AM";"Market Transaction";61101.78;399267361.88
11.2117;"Market Transaction";61101.78;399267361.88

为什么要打印不匹配的行，我该如何抑制它？

Answer 1

更改脚本以在 BEGIN 中包含分隔符堵塞。

脚本内容:

BEGIN {
FS=";"
OFS=";"
}
/Market Transaction/ {
    split($1, itemdate, " ");
    tmp = itemdate[2];
    split(tmp, hms, ":");
    timestamp = hms[3] + (hms[2] * 60) + (hms[1] * 3600);
    if (itemdate[3] == "AM")
       timestamp += 12 * 3600;
    timestamp /= 3600.0;
    $1 = timestamp;
    print;
}