如何在Linux中为日期变量添加时间？

debugcn 发表于 Dev

欧姆

尝试了这个但是失败了

now=$(date +%Y%m%d%H%M%S)
past=$(date +%Y%m%d%H%M%S -d "${now} -5minutes")
echo $past

结果：

date: invalid date ‘20200120175610 -5minutes’

muru

看来GNU日期无法解析该格式的时间戳。前导部分需要一年的时间：

% date +%Y%m%d%H%M%S -d 20200120175610 --debug
date: parsed number part: (Y-M-D) 2020012017-56-10
date: input timezone: system default
date: warning: using midnight as starting time: 00:00:00
date: error: invalid date/time value:
date:     user provided time: '(Y-M-D) 2020012017-56-10 00:00:00'
date:        normalized time: '(Y-M-D) 2020012021-08-10 00:00:00'
date:                                  ---- --
date:      possible reasons:
date:        numeric values overflow;
date:        missing timezone
date: invalid date ‘20200120175610’

如果没有出错，那么它可能不会溢出，但仍未达到您的期望：

% date +%Y%m%d%H%M%S -d "20200120181002 -5minutes" --debug
date: parsed hybrid part: -5 minutes
date: input timezone: system default
date: warning: using midnight as starting time: 00:00:00
date: starting date/time: '(Y-M-D) 2020012018-10-02 00:00:00'
date: '(Y-M-D) 2020012018-10-02 00:00:00' = 63745360147926000 epoch-seconds
date: after time adjustment (+0 hours, -5 minutes, +0 seconds, +0 ns),
date:     new time = 63745360147925700 epoch-seconds
date: timezone: system default
date: final: 63745360147925700.000000000 (epoch-seconds)
date: final: (Y-M-D) 2020012018-10-01 14:55:00 (UTC)
date: final: (Y-M-D) 2020012018-10-01 23:55:00 (UTC+09)
20200120181001235500

使用其他时间戳格式。我建议使用ISO-8601，并在输出时根据需要重新格式化：

% now=$(date --iso-8601=seconds)
% past=$(date -d "$now - 5 minutes" --iso-8601=seconds)
% printf "%s\n" "$now" "$past"
2020-01-20T18:29:50+09:00
2020-01-20T18:24:50+09:00
% date -d "$past" +%Y%m%d%H%M%S
20200120182450

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