blocks|key|804153|text|awk版本可能是最好的选择，但如果您首先使用tr压缩重复，您也可以使用cut|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|804154|ps+axu+%7C+grep+jbos[s]+%7C+tr+-s+'+'+%7C+cut+-d'+'+-f5
#++++++++%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E+++%5E%5E%5E%5E%5E%5E%5E%5E%5E+++%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E%5E
#++++++++++++++%7C++++++++++++%7C+++++++++++++%7C
#++++++++++++++%7C++++++++++++%7C+++++++get+5th+field
#++++++++++++++%7C++++++++++++%7C
#++++++++++++++%7C++++++++squeeze+spaces
#++++++++++++++%7C
#++++++++avoid+grep+itself+to+appear+in+the+list|code-block|syntax|javascript|804155|entityMap^0|0|3|M|2|Z|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|L|$]]

<code>awk</code> version is probably the best way to go, but you can also use <code>cut</code> if you firstly squeeze the repeats with <code>tr</code>:

<pre class="lang-sh prettyprint-override"><code>ps axu | grep jbos[s] | tr -s ' ' | cut -d' ' -f5
# ^^^^^^^^^^^^ ^^^^^^^^^ ^^^^^^^^^^^^^
# | | |
# | | get 5th field
# | |
# | squeeze spaces
# |
# avoid grep itself to appear in the list
</code></pre>

blocks|key|804244|text|为此，我喜欢使用tr+-s命令|type|unstyled|depth|inlineStyleRanges|entityRanges|data|804245|+ps+aux+%7C+tr+-s+[:blank:]+%7C+cut+-d'+'+-f3|code-block|syntax|javascript|804246|这会将所有空格压缩到1个空格。这样，告诉cut使用一个空格作为分隔符，就像预期的那样。|804247|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I like to use the tr -s command for this

<pre><code> ps aux | tr -s [:blank:] | cut -d' ' -f3
</code></pre>

This squeezes all white spaces down to 1 space. This way telling cut to use a space as a delimiter is honored as expected.

blocks|key|588472|text|我将提名tr+-s+[:blank:]作为最佳答案。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|588473|为什么我们要使用cut？它有一个神奇的命令，说“我们需要第三个字段和它后面的每个字段，忽略前两个字段”。|588474|cat+log+%7C+tr+-s+[:blank:]+%7Ccut+-d'+'+-f+3-+|code-block|syntax|javascript|588475|我不相信在awk或perl+split中有类似的命令，我们不知道会有多少个字段，也就是输出第三个字段到字段X。|588476|entityMap^0|4|F|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|T|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|V|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

I am going to nominate <code>tr -s [:blank:]</code> as the best answer.

Why do we want to use cut? It has the magic command that says "we want the third field and every field after it, omitting the first two fields"

<pre><code>cat log | tr -s [:blank:] |cut -d' ' -f 3- 
</code></pre>

I do not believe there is an equivalent command for awk or perl split where we do not know how many fields there will be, ie out put the 3rd field through field X.

blocks|key|804103|text|绕过这个问题的一种方法是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|804104|$ps+axu+%7C+grep+jboss+%7C+sed+'s/\s\%2B/+/g'+%7C+cut+-d'+'+-f3|code-block|syntax|javascript|804105|用一个空格替换多个连续的空格。|804106|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

One way around this is to go:

<pre><code>$ps axu | grep jboss | sed 's/\s\+/ /g' | cut -d' ' -f3
</code></pre>

to replace multiple consecutive spaces with a single one.

blocks|key|803898|text|就我个人而言，我倾向于使用awk来做这样的工作。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|803899|ps+axu%7C+grep+jboss+%7C+grep+-v+grep+%7C+awk+'{print+$5}'|code-block|syntax|javascript|803900|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Personally, I tend to use awk for jobs like this. For example:

<pre><code>ps axu| grep jboss | grep -v grep | awk '{print $5}'
</code></pre>

blocks|key|804371|text|作为另一种选择，总是有perl：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|804372|ps+aux+%7C+perl+-lane+'print+$F[3]'|code-block|syntax|javascript|804373|或者，如果您想获取从字段#3开始的所有字段(如上面的答案之一所述)：|804374|ps+aux+%7C+perl+-lane+'print+@F[3+..+scalar+@F]'|804375|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

As an alternative, there is always perl:

<pre><code>ps aux | perl -lane 'print $F[3]'
</code></pre>

Or, if you want to get all fields starting at field #3 (as stated in one of the answers above):

<pre><code>ps aux | perl -lane 'print @F[3 .. scalar @F]'
</code></pre>

blocks|key|588712|text|如果您想从ps输出中挑选列，那么有什么理由不使用-o呢？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|588713|例如：|588714|ps+ax+-o+pid,vsz
ps+ax+-o+pid,cmd|code-block|syntax|javascript|588715|分配的最小列宽，没有填充，只有一个空格字段分隔符。|588716|ps+ax+--no-headers+-o+pid:1,vsz:1,cmd

3443+24600+-bash
8419+0+[xfsalloc]
8420+0+[xfs_mru_cache]
8602+489316+/usr/sbin/apache2+-k+start
12821+497240+/usr/sbin/apache2+-k+start
12824+497132+/usr/sbin/apache2+-k+start|588717|Pid和vsz给定10个字符宽度，1个空间字段分隔符。|588718|ps+ax+--no-headers+-o+pid:10,vsz:10,cmd

++3443++++++24600+-bash
++8419++++++++++0+[xfsalloc]
++8420++++++++++0+[xfs_mru_cache]
++8602+++++489316+/usr/sbin/apache2+-k+start
+12821+++++497240+/usr/sbin/apache2+-k+start
+12824+++++497132+/usr/sbin/apache2+-k+start|588719|在脚本中使用：|588720|oldpid=12824
echo+"PID:+${oldpid}"
echo+"Command:+$(ps+-ho+cmd+${oldpid})"|588721|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|11|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|13|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|U|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|V|$]]

If you want to pick columns from a ps output, any reason to not use -o?

e.g.

<pre><code>ps ax -o pid,vsz
ps ax -o pid,cmd
</code></pre>

Minimum column width allocated, no padding, only single space field separator.

<pre><code>ps ax --no-headers -o pid:1,vsz:1,cmd

3443 24600 -bash
8419 0 [xfsalloc]
8420 0 [xfs_mru_cache]
8602 489316 /usr/sbin/apache2 -k start
12821 497240 /usr/sbin/apache2 -k start
12824 497132 /usr/sbin/apache2 -k start
</code></pre>

Pid and vsz given 10 char width, 1 space field separator.

<pre><code>ps ax --no-headers -o pid:10,vsz:10,cmd

 3443 24600 -bash
 8419 0 [xfsalloc]
 8420 0 [xfs_mru_cache]
 8602 489316 /usr/sbin/apache2 -k start
 12821 497240 /usr/sbin/apache2 -k start
 12824 497132 /usr/sbin/apache2 -k start
</code></pre>

Used in a script:-

<pre><code>oldpid=12824
echo "PID: ${oldpid}"
echo "Command: $(ps -ho cmd ${oldpid})"
</code></pre>

blocks|key|804201|text|另一种方法，如果您必须使用cut命令|type|unstyled|depth|inlineStyleRanges|entityRanges|data|804202|ps+axu+%7C+grep+[j]boss+%7Cawk+'$1=$1'%7Ccut+-d'+'+-f5|code-block|syntax|javascript|804203|在Solaris中，将awk替换为nawk或/usr/xpg4/bin/awk|offset|length|style|CODE|804204|entityMap^0|0|0|H|4|M|H|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

Another way if you must use cut command

<pre><code>ps axu | grep [j]boss |awk '$1=$1'|cut -d' ' -f5
</code></pre>

In Solaris, replace awk with <code>nawk</code> or <code>/usr/xpg4/bin/awk</code>

blocks|key|804340|text|我仍然喜欢Perl处理带有空格的字段的方式。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|804341|第一个字段是$F。|804342|$+ps+axu+%7C+grep+dbus+%7C+perl+-lane+'print+$F[4]'|code-block|syntax|javascript|804343|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I still like the way Perl handles fields with white space. 
First field is $F[0].

<pre><code>$ ps axu | grep dbus | perl -lane 'print $F[4]'
</code></pre>

blocks|key|804430|text|我的方法是将PID存储到/tmp中的一个文件中，然后使用ssh的-S选项查找正确的进程。这可能是一种误用，但对我来说很有效。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|804431|#!/bin/bash

TARGET_REDIS=${1:-redis.someserver.com}
PROXY="proxy.somewhere.com"

LOCAL_PORT=${2:-6379}

if+[+"$1"+==+"stop"+]+;+then
++++kill+`cat+/tmp/sshTunel${LOCAL_PORT}-pid`
++++exit
fi

set+-x

ssh+-f+-i+~/.ssh/aws.pem+centos@$PROXY+-L+$LOCAL_PORT:$TARGET_REDIS:6379+-N+-S+/tmp/sshTunel$LOCAL_PORT++##+AWS+DocService+dev,+DNS+alias
#+SSH_PID=$!+##+Only+works+with+&
SSH_PID=`ps+aux+%7C+grep+sshTunel${LOCAL_PORT}+%7C+grep+-v+grep+%7C+awk+'{print+$2}'`
echo+$SSH_PID+>+/tmp/sshTunel${LOCAL_PORT}-pid|code-block|syntax|javascript|804432|更好的方法可能是在终止SSH_PID之前查询它，因为文件可能已经过时，它会杀死错误的进程。|804433|entityMap^0|S|3|W|2|0|0|B|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

My approach is to store the PID to a file in /tmp, and to find the right process using the <code>-S</code> option for <code>ssh</code>. That might be a misuse but works for me.

<pre><code>#!/bin/bash

TARGET_REDIS=${1:-redis.someserver.com}
PROXY="proxy.somewhere.com"

LOCAL_PORT=${2:-6379}

if [ "$1" == "stop" ] ; then
 kill `cat /tmp/sshTunel${LOCAL_PORT}-pid`
 exit
fi

set -x

ssh -f -i ~/.ssh/aws.pem centos@$PROXY -L $LOCAL_PORT:$TARGET_REDIS:6379 -N -S /tmp/sshTunel$LOCAL_PORT ## AWS DocService dev, DNS alias
# SSH_PID=$! ## Only works with &amp;
SSH_PID=`ps aux | grep sshTunel${LOCAL_PORT} | grep -v grep | awk '{print $2}'`
echo $SSH_PID &gt; /tmp/sshTunel${LOCAL_PORT}-pid
</code></pre>

Better approach might be to query for the <code>SSH_PID</code> right before killing it, since the file might be stale and it would kill a wrong process.

Is there any way to specify a field delimiter for more spaces with the cut command? (like " "+) ?
For example: In the following string, I like to reach value '3744', what field delimiter I should say?

<pre><code>$ps axu | grep jboss

jboss 2574 0.0 0.0 3744 1092 ? S Aug17 0:00 /bin/sh /usr/java/jboss/bin/run.sh -c example.com -b 0.0.0.0
</code></pre>

<code>cut -d' '</code> is not what I want, for it's only for one single space. 
<code>awk</code> is not what I am looking for either, but how to do with 'cut'?

thanks.

How to specify more spaces for the delimiter using cut?

Solaris

Perl

有没有办法用cut命令为更多的空格指定一个字段分隔符？(像“"+)？例如:在下面的字符串中，我喜欢达到值'3744'，我应该说哪个字段分隔符？$ps axu | grep jbossjboss     2574  0.0  0.0   3744  1092 ?        S    Aug17   0:00 /bin/sh /usr/java/jboss/bin/run.sh -c exampl

问如何使用cut为分隔符指定更多的空格？
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