Question

我很难从我在后台运行的shell（ksh）脚本中隐藏控制台消息。

我已经尝试将其移动到/ dev / null但它似乎没有工作。以下是脚本中的一行：

pid=`/usr/local/bin/lsof | grep 16752 | grep LISTEN |awk '{print $2}'` > /dev/null 2>&1

我开始播放剧本后的示例：

$ lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.
lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.

$ ls -lsof: WARNING: /home2/s499929/.lsof_ktazd2250 was updated.

关于我缺少的任何想法？

Answer 1

/usr/local/bin/lsof 2>/dev/null | grep 16752 | grep LISTEN |awk '{print $2}'

Answer 2

也许您需要重定向实际lsof命令的输出而不是awk？

Answer 3

您正在重定向变量赋值的输出。由于变量赋值不会产生任何输出，因此您的重定向没有做任何事情。

反引号捕获命令的标准输出;你需要重定向该命令的stderr，这意味着重定向需要在反引号之间。

我的第一个想法是这样做：

pid=`/usr/local/bin/lsof | grep 16752 | grep LISTEN | awk '{print $2}' 2>/dev/null`

但只重定向awk命令的stderr。您需要丢弃整个管道的stderr：

pid=`(/usr/local/bin/lsof | grep 16752 | grep LISTEN | awk '{print $2}') 2>/dev/null`

但我个人更喜欢$(...)反对：

pid=$((/usr/local/bin/lsof | grep 16752 | grep LISTEN | awk '{print $2}') 2>/dev/null)

（请注意，我只是重定向stderr，而不是stdout;你需要stdout来进行变量赋值。）

Shell脚本隐藏控制台消息？

3 个答案: