小编Chr*_*ris的帖子

我想从 jq 输出下面打印成员和 id 的值：

$ cat test_|jq -r '.[] | select(.name=="AAA") | .'
{
  "name": "AAA",
  "members": 10,
  "profiles": 0,
  "templates": 0,
  "ldapGroups": 0,
  "ldapMembers": 0,
  "id": "20"
}

不幸的是，它仅适用于其中之一：

$ cat test_|jq -r '.[] | select(.name=="AAA") | .members'
10

用 +" "+ 我得到错误：

$ cat test_|jq -r '.[] | select(.name=="AAA") | .members+" "+.id'
jq: error: number and string cannot be added

有人可以解释一下下面的警告吗？

输入文件是：

{
 "env": "DC",
 "hosts" :
[
{
  "apt_update_last_success": "1495991703",
  "architecture": "amd64",
  "hostname": "h1"
},
{
  "apt_update_last_success": "1495991703",
  "architecture": "amd64",
  "hostname": "h2"
},
{
  "apt_update_last_success": "1496045706",
  "architecture": "amd64",
  "hostname": "h3"
},
{
  "apt_update_last_success": "1496045705",
  "architecture": "amd64",
  "hostname": "h4"
},
{
  "apt_update_last_success": "1496049305",
  "architecture": "amd64",
  "hostname": "h5"
},
{
  "apt_update_last_success": "1496049307",
  "architecture": "amd64",
  "hostname": "h6"
}
]
}

jq 命令返回预期的内容，但也打印警告我不知道为什么：

$ jq -r '.[][] | select(.hostname=="h6")' ddd.json
jq: error: Cannot iterate over string
{
  "apt_update_last_success": "1496049307",
  "architecture": "amd64",
  "hostname": "h6" …

我有一个输入日志表格:

system 2018-02-05 04:15:49 :: aaaaaaaaaaaaa  
system 2018-02-05 04:15:51 :: aaaaaaaaaaaaa  
system 2018-02-05 04:15:51 :: aaaaaaaaaaaaa  
system 2018-02-05 04:15:52 :: aaaaaaaaaaaaa  
system 2018-02-05 04:15:53 :: aaaaaaaaaaaaa  
system 2018-02-05 04:20:06 :: ccccccccccccc
system 2018-02-05 04:21:10 :: bbbbbbbbbbbbb
system 2018-02-05 04:21:10 :: ccccccccccccc
system 2018-02-05 04:21:10 :: ccccccccccccc
system 2018-02-05 04:21:10 :: ccccccccccccc
system 2018-02-05 04:23:49 :: bbbbbbbbbbbbb
system 2018-02-05 04:23:49 :: ccccccccccccc

并希望用空行分隔每个时间块.上述输入的预期输出将是:

system 2018-02-05 04:15:49 :: aaaaaaaaaaaaa

system 2018-02-05 04:15:51 :: aaaaaaaaaaaaa  
system 2018-02-05 04:15:51 :: aaaaaaaaaaaaa  

system 2018-02-05 04:15:52 …

bash 中的小写/大写有一个很好的功能：

$ string="A FEW WORDS"
$ echo "${string,}"
a FEW WORDS
$ echo "${string,,}"
a few words
$ echo "${string,,[AEIUO]}"
a FeW WoRDS

有人知道类似的方法将变量上每个单词中的第一个字符设置为大写，并将每个单词中的其余字符设置为小写吗？

$ echo "${string,,[^.]}"
a few words
$ echo "${string,,[^]}"
A FEW WORDS
$ echo "${string,,.}"
A FEW WORDS
$ echo "${string,,^.}"
A FEW WORDS
$ echo "${string,,^?}"
A FEW WORDS
$ echo "${string,,?}"
a few words