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Merge remote-tracking branch 'LCTT/master'
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0a4fb8601e
@ -1,83 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Huawei ban could complicate 5G deployment)
|
||||
[#]: via: (https://www.networkworld.com/article/3575408/huawei-ban-could-complicate-5g-deployment.html)
|
||||
[#]: author: (Jon Gold https://www.networkworld.com/author/Jon-Gold/)
|
||||
|
||||
Huawei ban could complicate 5G deployment
|
||||
======
|
||||
Bans on Huawei, ZTE mean fewer choices for wireless carriers building 5G services
|
||||
Vertigo3D / Getty Images
|
||||
|
||||
As carriers race to build out their 5G networks, options for buying the gear they need are fewer in the U.S. than in other countries thanks to federal pressure, which could be slowing deployments.
|
||||
|
||||
### 5G resources
|
||||
|
||||
* [What is 5G? Fast wireless technology for enterprises and phones][1]
|
||||
* [How 5G frequency affects range and speed][2]
|
||||
* [Private 5G can solve some problems that Wi-Fi can’t][3]
|
||||
* [Private 5G keeps Whirlpool driverless vehicles rolling][4]
|
||||
* [5G can make for cost-effective private backhaul][5]
|
||||
* [CBRS can bring private 5G to enterprises][6]
|
||||
|
||||
|
||||
|
||||
China-based Huawei and ZTE were both banned from providing equipment to the government itself in the Defense Authorization Act of 2018, and a general import ban followed shortly thereafter. That has changed the competitive landscape considerably, and raises questions about how the shape of 5G in America could change as a consequence.
|
||||
|
||||
Michael Porowski , a Gartner analyst, said it’s possible, though not completely clear, that the restriction on where carriers can buy their 5G equipment is slowing deployment.
|
||||
|
||||
“There’s still an ample number of suppliers – Ericsson, Nokia, Samsung,” he said. Both ZTE and Huawei are more economical options, he said, and “if they were available, you might see a bit faster adoption.”
|
||||
|
||||
[[Get regularly scheduled insights by signing up for Network World newsletters.]][7]
|
||||
|
||||
There’s a sense in the industry that Huawei equipment is both sophisticated and priced to move, according to Christian Renaud, research director at 451 Research, but there’s also no clear alternative that carriers will gravitate to in the absence of Huawei.
|
||||
|
||||
“Here, you’ll have carriers that have standardized on Nokia or Ericsson,” he said. “[And] it’s too soon to tell who’s most sophisticated because deployments are so limited.”
|
||||
|
||||
That contention is borne out by coverage maps from the carriers themselves. While they have been quick to trumpet the presence of 5G service in many U.S. markets, the actual geographic coverage is mostly restricted to public spaces in the urban cores of major cities. The lion’s share of 5G deployment, in short, is yet to come.
|
||||
|
||||
There are good reasons for slow deployment. 5G access points have to be deployed far more densely than earlier generation wireless technology, making the process more involved and time-consuming. There’s also the issue that the number of currently available 5G user devices is vanishingly small.
|
||||
|
||||
“It’s like saying ‘I’ve got this eight-lane superhighway,’ before someone has invented cars,” said Renaud.
|
||||
|
||||
Part of the current goal for equipment vendors is demonstrating the potentials of 5G through private deployments that use the technology for backhaul, supporting [IoT][8] and other link use cases specific to a single enterprise.
|
||||
|
||||
“[The equipment vendors] are all pushing hard on the private piece, and then they can use that to say, ‘Look, I’m working the Brooklyn dockyards or something in a private 5G network, so … if I can do that I can run people’s YouTube connections,’” Renaud said.
|
||||
|
||||
An unfortunate result of the China ban might be a splintering of the specifications that vendors follow to meet 5G requirements. If non-China vendors have to make one version for markets where Huawei and ZTE are allowed and a different version for places they are not, it could create a new headache for them, according to Renaud.
|
||||
|
||||
“That’ll shift the burden of costs to the device makers to try to support the different carrier implementations," he said. “We’ll have created nontechnical barriers.” And those, in turn, could cause customer experience to suffer.
|
||||
|
||||
But 5G has embraced a move toward greater interoperability with [open radio access network technology][9] that standardizes the software interfaces between layers of the 5G stack. The push is embraced by carriers and equipment vendors alike, making interoperability more likely, which could draw in even more players in the future.
|
||||
|
||||
Of course, even with pervasive interoperability, equipment makers will still try to build customer dependency. “There’s always going to be a tug of war between vendors trying to lock in customers and customers trying to stay vendor-neutral,” he said. “That’s not going to change a lot. [But] we’ve obviously seen a move toward trying to be more open.”
|
||||
|
||||
Join the Network World communities on [Facebook][10] and [LinkedIn][11] to comment on topics that are top of mind.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.networkworld.com/article/3575408/huawei-ban-could-complicate-5g-deployment.html
|
||||
|
||||
作者：[Jon Gold][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.networkworld.com/author/Jon-Gold/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://www.networkworld.com/article/3203489/what-is-5g-fast-wireless-technology-for-enterprises-and-phones.html
|
||||
[2]: https://www.networkworld.com/article/3568253/how-5g-frequency-affects-range-and-speed.html
|
||||
[3]: https://www.networkworld.com/article/3568614/private-5g-can-solve-some-enterprise-problems-that-wi-fi-can-t.html
|
||||
[4]: https://www.networkworld.com/article/3488799/private-5g-keeps-whirlpool-driverless-vehicles-rolling.html
|
||||
[5]: https://www.networkworld.com/article/3570724/5g-can-make-for-cost-effective-private-backhaul.html
|
||||
[6]: https://www.networkworld.com/article/3529291/cbrs-wireless-can-bring-private-5g-to-enterprises.html
|
||||
[7]: https://www.networkworld.com/newsletters/signup.html
|
||||
[8]: https://www.networkworld.com/article/3207535/what-is-iot-the-internet-of-things-explained.html
|
||||
[9]: https://www.networkworld.com/article/3574977/carriers-vendors-work-to-promote-5g-network-flexibility-with-open-standards.html
|
||||
[10]: https://www.facebook.com/NetworkWorld/
|
||||
[11]: https://www.linkedin.com/company/network-world
|
||||
@ -1,287 +0,0 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Advance your awk skills with two easy tutorials)
|
||||
[#]: via: (https://opensource.com/article/19/10/advanced-awk)
|
||||
[#]: author: (Dave Neary https://opensource.com/users/dneary)
|
||||
|
||||
Advance your awk skills with two easy tutorials
|
||||
======
|
||||
Go beyond one-line awk scripts with mail merge and word counting.
|
||||
![a checklist for a team][1]
|
||||
|
||||
Awk is one of the oldest tools in the Unix and Linux user's toolbox. Created in the 1970s by Alfred Aho, Peter Weinberger, and Brian Kernighan (the A, W, and K of the tool's name), awk was created for complex processing of text streams. It is a companion tool to sed, the stream editor, which is designed for line-by-line processing of text files. Awk allows more complex structured programs and is a complete programming language.
|
||||
|
||||
This article will explain how to use awk for more structured and complex tasks, including a simple mail merge application.
|
||||
|
||||
### Awk program structure
|
||||
|
||||
An awk script is made up of functional blocks surrounded by **{}** (curly brackets). There are two special function blocks, **BEGIN** and **END**, that execute before processing the first line of the input stream and after the last line is processed. In between, blocks have the format:
|
||||
|
||||
|
||||
```
|
||||
`pattern { action statements }`
|
||||
```
|
||||
|
||||
Each block executes when the line in the input buffer matches the pattern. If no pattern is included, the function block executes on every line of the input stream.
|
||||
|
||||
Also, the following syntax can be used to define functions in awk that can be called from any block:
|
||||
|
||||
|
||||
```
|
||||
`function name(parameter list) { statements }`
|
||||
```
|
||||
|
||||
This combination of pattern-matching blocks and functions allows the developer to structure awk programs for reuse and readability.
|
||||
|
||||
### How awk processes text streams
|
||||
|
||||
Awk reads text from its input file or stream one line at a time and uses a field separator to parse it into a number of fields. In awk terminology, the current buffer is a _record_. There are a number of special variables that affect how awk reads and processes a file:
|
||||
|
||||
* **FS** (field separator): By default, this is any whitespace (spaces or tabs)
|
||||
* **RS** (record separator): By default, a newline (**\n**)
|
||||
* **NF** (number of fields): When awk parses a line, this variable is set to the number of fields that have been parsed
|
||||
* **$0:** The current record
|
||||
* **$1, $2, $3, etc.:** The first, second, third, etc. field from the current record
|
||||
* **NR** (number of records): The number of records that have been parsed so far by the awk script
|
||||
|
||||
|
||||
|
||||
There are many other variables that affect awk's behavior, but this is enough to start with.
|
||||
|
||||
### Awk one-liners
|
||||
|
||||
For a tool so powerful, it's interesting that most of awk's usage is basic one-liners. Perhaps the most common awk program prints selected fields from an input line from a CSV file, a log file, etc. For example, the following one-liner prints a list of usernames from **/etc/passwd**:
|
||||
|
||||
|
||||
```
|
||||
`awk -F":" '{print $1 }' /etc/passwd`
|
||||
```
|
||||
|
||||
As mentioned above, **$1** is the first field in the current record. The **-F** option sets the FS variable to the character **:**.
|
||||
|
||||
The field separator can also be set in a BEGIN function block:
|
||||
|
||||
|
||||
```
|
||||
`awk 'BEGIN { FS=":" } {print $1 }' /etc/passwd`
|
||||
```
|
||||
|
||||
In the following example, every user whose shell is not **/sbin/nologin** can be printed by preceding the block with a pattern match:
|
||||
|
||||
|
||||
```
|
||||
`awk 'BEGIN { FS=":" } ! /\/sbin\/nologin/ {print $1 }' /etc/passwd`
|
||||
```
|
||||
|
||||
### Advanced awk: Mail merge
|
||||
|
||||
Now that you have some of the basics, try delving deeper into awk with a more structured example: creating a mail merge.
|
||||
|
||||
A mail merge uses two files, one (called in this example **email_template.txt**) containing a template for an email you want to send:
|
||||
|
||||
|
||||
```
|
||||
From: Program committee <[pc@event.org][2]>
|
||||
To: {firstname} {lastname} <{email}>
|
||||
Subject: Your presentation proposal
|
||||
|
||||
Dear {firstname},
|
||||
|
||||
Thank you for your presentation proposal:
|
||||
{title}
|
||||
|
||||
We are pleased to inform you that your proposal has been successful! We
|
||||
will contact you shortly with further information about the event
|
||||
schedule.
|
||||
|
||||
Thank you,
|
||||
The Program Committee
|
||||
```
|
||||
|
||||
And the other is a CSV file (called **proposals.csv**) with the people you want to send the email to:
|
||||
|
||||
|
||||
```
|
||||
firstname,lastname,email,title
|
||||
Harry,Potter,[hpotter@hogwarts.edu][3],"Defeating your nemesis in 3 easy steps"
|
||||
Jack,Reacher,[reacher@covert.mil][4],"Hand-to-hand combat for beginners"
|
||||
Mickey,Mouse,[mmouse@disney.com][5],"Surviving public speaking with a squeaky voice"
|
||||
Santa,Claus,[sclaus@northpole.org][6],"Efficient list-making"
|
||||
```
|
||||
|
||||
You want to read the CSV file, replace the relevant fields in the first file (skipping the first line), then write the result to a file called **acceptanceN.txt**, incrementing **N** for each line you parse.
|
||||
|
||||
Write the awk program in a file called **mail_merge.awk**. Statements are separated by **;** in awk scripts. The first task is to set the field separator variable and a couple of other variables the script needs. You also need to read and discard the first line in the CSV, or a file will be created starting with _Dear firstname_. To do this, use the special function **getline** and reset the record counter to 0 after reading it.
|
||||
|
||||
|
||||
```
|
||||
BEGIN {
|
||||
FS=",";
|
||||
template="email_template.txt";
|
||||
output="acceptance";
|
||||
getline;
|
||||
NR=0;
|
||||
}
|
||||
```
|
||||
|
||||
The main function is very straightforward: for each line processed, a variable is set for the various fields—**firstname**, **lastname**, **email**, and **title**. The template file is read line by line, and the function **sub** is used to substitute any occurrence of the special character sequences with the value of the relevant variable. Then the line, with any substitutions made, is output to the output file.
|
||||
|
||||
Since you are dealing with the template file and a different output file for each line, you need to clean up and close the file handles for these files before processing the next record.
|
||||
|
||||
|
||||
```
|
||||
{
|
||||
# Read relevant fields from input file
|
||||
firstname=$1;
|
||||
lastname=$2;
|
||||
email=$3;
|
||||
title=$4;
|
||||
|
||||
# Set output filename
|
||||
outfile=(output NR ".txt");
|
||||
|
||||
# Read a line from template, replace special fields, and
|
||||
# print result to output file
|
||||
while ( (getline ln < template) > 0 )
|
||||
{
|
||||
sub(/{firstname}/,firstname,ln);
|
||||
sub(/{lastname}/,lastname,ln);
|
||||
sub(/{email}/,email,ln);
|
||||
sub(/{title}/,title,ln);
|
||||
print(ln) > outfile;
|
||||
}
|
||||
|
||||
# Close template and output file in advance of next record
|
||||
close(outfile);
|
||||
close(template);
|
||||
}
|
||||
```
|
||||
|
||||
You're done! Run the script on the command line with:
|
||||
|
||||
|
||||
```
|
||||
`awk -f mail_merge.awk proposals.csv`
|
||||
```
|
||||
|
||||
or
|
||||
|
||||
|
||||
```
|
||||
`awk -f mail_merge.awk < proposals.csv`
|
||||
```
|
||||
|
||||
and you will find text files generated in the current directory.
|
||||
|
||||
### Advanced awk: Word frequency count
|
||||
|
||||
One of the most powerful features in awk is the associative array. In most programming languages, array entries are typically indexed by a number, but in awk, arrays are referenced by a key string. You could store an entry from the file _proposals.txt_ from the previous section. For example, in a single associative array, like this:
|
||||
|
||||
|
||||
```
|
||||
proposer["firstname"]=$1;
|
||||
proposer["lastname"]=$2;
|
||||
proposer["email"]=$3;
|
||||
proposer["title"]=$4;
|
||||
```
|
||||
|
||||
This makes text processing very easy. A simple program that uses this concept is the idea of a word frequency counter. You can parse a file, break out words (ignoring punctuation) in each line, increment the counter for each word in the line, then output the top 20 words that occur in the text.
|
||||
|
||||
First, in a file called **wordcount.awk**, set the field separator to a regular expression that includes whitespace and punctuation:
|
||||
|
||||
|
||||
```
|
||||
BEGIN {
|
||||
# ignore 1 or more consecutive occurrences of the characters
|
||||
# in the character group below
|
||||
FS="[ .,:;()<>{}@!\"'\t]+";
|
||||
}
|
||||
```
|
||||
|
||||
Next, the main loop function will iterate over each field, ignoring any empty fields (which happens if there is punctuation at the end of a line), and increment the word count for the words in the line.
|
||||
|
||||
|
||||
```
|
||||
{
|
||||
for (i = 1; i <= NF; i++) {
|
||||
if ($i != "") {
|
||||
words[$i]++;
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Finally, after the text is processed, use the END function to print the contents of the array, then use awk's capability of piping output into a shell command to do a numerical sort and print the 20 most frequently occurring words:
|
||||
|
||||
|
||||
```
|
||||
END {
|
||||
sort_head = "sort -k2 -nr | head -n 20";
|
||||
for (word in words) {
|
||||
printf "%s\t%d\n", word, words[word] | sort_head;
|
||||
}
|
||||
close (sort_head);
|
||||
}
|
||||
```
|
||||
|
||||
Running this script on an earlier draft of this article produced this output:
|
||||
|
||||
|
||||
```
|
||||
[[dneary@dhcp-49-32.bos.redhat.com][7]]$ awk -f wordcount.awk < awk_article.txt
|
||||
the 79
|
||||
awk 41
|
||||
a 39
|
||||
and 33
|
||||
of 32
|
||||
in 27
|
||||
to 26
|
||||
is 25
|
||||
line 23
|
||||
for 23
|
||||
will 22
|
||||
file 21
|
||||
we 16
|
||||
We 15
|
||||
with 12
|
||||
which 12
|
||||
by 12
|
||||
this 11
|
||||
output 11
|
||||
function 11
|
||||
```
|
||||
|
||||
### What's next?
|
||||
|
||||
If you want to learn more about awk programming, I strongly recommend the book [_Sed and awk_][8] by Dale Dougherty and Arnold Robbins.
|
||||
|
||||
One of the keys to progressing in awk programming is mastering "extended regular expressions." Awk offers several powerful additions to the sed [regular expression][9] syntax you may already be familiar with.
|
||||
|
||||
Another great resource for learning awk is the [GNU awk user guide][10]. It has a full reference for awk's built-in function library, as well as lots of examples of simple and complex awk scripts.
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/10/advanced-awk
|
||||
|
||||
作者：[Dave Neary][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://opensource.com/users/dneary
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/checklist_hands_team_collaboration.png?itok=u82QepPk (a checklist for a team)
|
||||
[2]: mailto:pc@event.org
|
||||
[3]: mailto:hpotter@hogwarts.edu
|
||||
[4]: mailto:reacher@covert.mil
|
||||
[5]: mailto:mmouse@disney.com
|
||||
[6]: mailto:sclaus@northpole.org
|
||||
[7]: mailto:dneary@dhcp-49-32.bos.redhat.com
|
||||
[8]: https://www.amazon.com/sed-awk-Dale-Dougherty/dp/1565922255/book
|
||||
[9]: https://en.wikibooks.org/wiki/Regular_Expressions/POSIX-Extended_Regular_Expressions
|
||||
[10]: https://www.gnu.org/software/gawk/manual/gawk.html
|
||||
@ -1,5 +1,5 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: ( )
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
|
||||
@ -0,0 +1,79 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (geekpi)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Huawei ban could complicate 5G deployment)
|
||||
[#]: via: (https://www.networkworld.com/article/3575408/huawei-ban-could-complicate-5g-deployment.html)
|
||||
[#]: author: (Jon Gold https://www.networkworld.com/author/Jon-Gold/)
|
||||
|
||||
华为禁令可能使 5G 部署复杂化
|
||||
======
|
||||
对华为、中兴的禁令意味着无线运营商建设 5G 服务的选择减少了。
|
||||
|
||||
随着运营商竞相建设他们的 5G 网络，由于联邦的压力，在美国购买所需设备的选择比其他国家少，这可能会减缓部署。
|
||||
|
||||
### 5G资源
|
||||
|
||||
* [什么是 5G？ 企业和手机的快速无线技术][1] 。
|
||||
* [5G 频率如何影响范围和速度][2]
|
||||
* [私有 5G 可以解决 Wi-Fi 不能解决的一些问题][3]
|
||||
* [私有 5G 让惠而浦无人驾驶汽车到来][4] 。
|
||||
* [5G 可使私有回传具有成本效益][5]
|
||||
* [CBRS 可以把私有 5G 带到企业][6]
|
||||
|
||||
|
||||
|
||||
在 2018 年的《国防授权法案》中，总部位于中国的华为和中兴通讯都被禁止向政府提供设备，随后不久，就是全面禁止进口。这大大改变了竞争格局，并引发了美国 5G 的形态可能因此而改变的问题。
|
||||
|
||||
Gartner 的分析师 Michael Porowski 表示，虽然还不完全清楚，但有可能运营商在哪里购买 5G 设备的限制正在减缓部署。
|
||||
|
||||
他说：”仍然有充足的供应商：爱立信、诺基亚、三星。中兴和华为都是更经济的选择。如果它们可用，你可能会看到更快的采用速度。”
|
||||
|
||||
451 Research 的研究总监 Christian Renaud 表示，业界有一种感觉，即华为设备既复杂又价格低廉，但在没有华为的情况下，运营商也没有明确的替代方案。
|
||||
|
||||
他说：”这里，会有运营商以诺基亚或爱立信为标准。（而且）现在判断谁最复杂还为时过早，因为部署是如此有限。”
|
||||
|
||||
这种争论在运营商本身的覆盖地图上得到证实。虽然他们很快就大肆宣传 5G 服务在美国许多市场的存在，但实际的地理覆盖范围大多局限于大城市核心区的公共场所。简而言之，大部分地区的 5G 部署还没有到来。
|
||||
|
||||
部署缓慢是有充分理由的。5G 接入点的部署密度要远高于早期一代无线技术，因此过程中涉及的内容更多，也更耗时。还有一个问题是，目前可用的 5G 用户设备数量还很少。
|
||||
|
||||
Renaud 说：”这就好比说， 在有人发明汽车之前，说”我已经有了这条八车道的超级高速公路“。“
|
||||
|
||||
设备供应商目前的部分目标是通过私人部署来展示 5G 的潜力，这些部署将该技术用回传，用于支持[物联网][8]和其他针对单个企业的链接场景。
|
||||
|
||||
Renaud 说：”（设备供应商）都在大力推动私有化这一块，然后他们可以利用这一点说，你看，我在私有化的 5G 这块做着布鲁克林造船厂之类的事情，所以，如果我能实现，我就可以运行人们的 YouTube 连接。“
|
||||
|
||||
中国禁令的一个不幸结果可能是供应商为满足 5G 要求而遵循的规范的分裂。Renaud 称，如果非中国供应商必须为允许华为和中兴的市场制作一个版本，而为不允许华为和中兴的地方制作不同的版本，这可能会给他们带来新的麻烦。
|
||||
|
||||
他说：”这将把成本负担转移到设备制造商身上，来试图支持不同的运营商实施。我们会造成非技术性的障碍。” 而这些，又会导致客户体验受到影响。
|
||||
|
||||
但是，5G 已经接受了一种拥有更高的互操作性的[开放无线接入网技术][9]，它将 5G 栈各层之间的软件接口标准化。运营商和设备商都接受了这一推动，使得互操作性更有可能，这可能会在未来吸引更多的玩家。
|
||||
|
||||
当然，即便是普遍的互操作性，设备制造商仍然会试图建立客户依赖性。他说”在试图锁定客户的供应商和试图保持供应商中立的客户之间，总是会有一场拉锯战。这不会有很大的改变。（但是）我们显然已经看到了试图更加开放的动向。”
|
||||
|
||||
加入 [Facebook][10] 和 [LinkedIn][11] 上的 Network World 社区，对热门话题进行评论。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://www.networkworld.com/article/3575408/huawei-ban-could-complicate-5g-deployment.html
|
||||
|
||||
作者：[Jon Gold][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[geekpi](https://github.com/geekpi)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.networkworld.com/author/Jon-Gold/
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://www.networkworld.com/article/3203489/what-is-5g-fast-wireless-technology-for-enterprises-and-phones.html
|
||||
[2]: https://www.networkworld.com/article/3568253/how-5g-frequency-affects-range-and-speed.html
|
||||
[3]: https://www.networkworld.com/article/3568614/private-5g-can-solve-some-enterprise-problems-that-wi-fi-can-t.html
|
||||
[4]: https://www.networkworld.com/article/3488799/private-5g-keeps-whirlpool-driverless-vehicles-rolling.html
|
||||
[5]: https://www.networkworld.com/article/3570724/5g-can-make-for-cost-effective-private-backhaul.html
|
||||
[6]: https://www.networkworld.com/article/3529291/cbrs-wireless-can-bring-private-5g-to-enterprises.html
|
||||
[8]: https://www.networkworld.com/article/3207535/what-is-iot-the-internet-of-things-explained.html
|
||||
[9]: https://www.networkworld.com/article/3574977/carriers-vendors-work-to-promote-5g-network-flexibility-with-open-standards.html
|
||||
[10]: https://www.facebook.com/NetworkWorld/
|
||||
[11]: https://www.linkedin.com/company/network-world
|
||||
@ -0,0 +1,272 @@
|
||||
[#]: collector: (lujun9972)
|
||||
[#]: translator: (wxy)
|
||||
[#]: reviewer: ( )
|
||||
[#]: publisher: ( )
|
||||
[#]: url: ( )
|
||||
[#]: subject: (Advance your awk skills with two easy tutorials)
|
||||
[#]: via: (https://opensource.com/article/19/10/advanced-awk)
|
||||
[#]: author: (Dave Neary https://opensource.com/users/dneary)
|
||||
|
||||
|
||||
通过两个简单的教程来提高你的 awk 技能
|
||||
======
|
||||
|
||||
> 超越单行的awk脚本，邮件合并和字数统计。
|
||||
!["一个团队的检查表"[1]
|
||||
|
||||
`awk` 是 Unix 和 Linux 用户工具箱中最古老的工具之一。`awk` 由 Alfred Aho、Peter Weinberger 和 Brian Kernighan（工具名称中的 A、W 和 K）在 20 世纪 70 年代创建，用于复杂的文本流处理。它是流编辑器 `sed` 的配套工具，后者是为逐行处理文本文件而设计的。`awk` 支持更复杂的结构化程序，是一种完整的编程语言。
|
||||
|
||||
本文将介绍如何使用 `awk` 完成更多结构化的复杂任务，包括一个简单的邮件合并程序。
|
||||
|
||||
### awk 的程序结构
|
||||
|
||||
`awk` 脚本是由 `{}`（大括号）包围的功能块组成，其中有两个特殊的功能块，`BEGIN` 和 `END`，它们在处理第一行输入流之前和最后一行处理之后执行。在这两者之间，块的格式为：
|
||||
|
||||
```
|
||||
模式 { 动作语句 }
|
||||
```
|
||||
|
||||
当输入缓冲区中的行与模式匹配时，每个块都会执行。如果没有包含模式，则函数块在输入流的每一行都会执行。
|
||||
|
||||
另外，以下语法可以用于在 `awk` 中定义可以从任何块中调用的函数。
|
||||
|
||||
```
|
||||
function 函数名(参数列表) { 语句 }
|
||||
```
|
||||
|
||||
这种模式匹配块和函数的组合允许开发者结构化 `awk` 程序，以便重用和可读。
|
||||
|
||||
### awk 如何处理文本流
|
||||
|
||||
`awk` 每次从输入文件或流中一行一行地读取文本，并使用字段分隔符将其解析成若干字段。在 `awk` 的术语中，当前的缓冲区是一个*记录*。有一些特殊的变量会影响 `awk` 读取和处理文件的方式：
|
||||
|
||||
* `FS`（<ruby>字段分隔符<rt>field separator</rt></ruby>）。默认情况下，这是任何空格字符（空格或制表符）。
|
||||
* `RS`（<ruby>记录分隔符<rt>record separator</rt></ruby>）。默认情况下是一个新行（`n`）。
|
||||
* `NF`（<ruby>字段数<rt>number of fields</rt></ruby>）。当 `awk` 解析一行时，这个变量被设置为已解析的字段数。
|
||||
* `$0:` 当前记录。
|
||||
* `$1`、`$2`、`$3` 等：当前记录的第一、第二、第三等字段。
|
||||
* `NR`（<ruby>记录数<rt>number of records</rt></ruby>）。迄今已被 `awk` 脚本解析的记录数。
|
||||
|
||||
影响 `awk` 行为的变量还有很多，但这已经足够开始了。
|
||||
|
||||
### 单行 awk 脚本
|
||||
|
||||
对于一个如此强大的工具来说，有趣的是，`awk` 的大部分用法都是基本的单行脚本。也许最常见的 `awk` 程序是打印 CSV 文件、日志文件等输入行中的选定字段。例如，下面的单行脚本从 `/etc/passwd` 中打印出一个用户名列表：
|
||||
|
||||
```
|
||||
awk -F":" '{print $1 }' /etc/passwd
|
||||
```
|
||||
|
||||
如上所述，`$1` 是当前记录中的第一个字段。`-F` 选项将 `FS` 变量设置为字符 `:`。
|
||||
|
||||
字段分隔符也可以在 `BEGIN` 函数块中设置：
|
||||
|
||||
```
|
||||
awk 'BEGIN { FS=":" } {print $1 }' /etc/passwd
|
||||
```
|
||||
|
||||
在下面的例子中，每一个 shell 不是 `/sbin/nologin` 的用户都可以通过在该块前面加上匹配模式来打印出来：
|
||||
|
||||
```
|
||||
awk 'BEGIN { FS=":" } ! /\/sbin\/nologin/ {print $1 }' /etc/passwd
|
||||
```
|
||||
|
||||
### awk 进阶：邮件合并
|
||||
|
||||
现在你已经掌握了一些基础知识，尝试用一个更具有结构化的例子来深入了解 `awk`：创建邮件合并。
|
||||
|
||||
邮件合并使用两个文件，其中一个文件（在本例中称为 `email_template.txt`）包含了你要发送的电子邮件的模板：
|
||||
|
||||
```
|
||||
From: Program committee <pc@event.org>
|
||||
To: {firstname} {lastname} <{email}>
|
||||
Subject: Your presentation proposal
|
||||
|
||||
Dear {firstname},
|
||||
|
||||
Thank you for your presentation proposal:
|
||||
{title}
|
||||
|
||||
We are pleased to inform you that your proposal has been successful! We
|
||||
will contact you shortly with further information about the event
|
||||
schedule.
|
||||
|
||||
Thank you,
|
||||
The Program Committee
|
||||
```
|
||||
|
||||
而另一个则是一个 CSV 文件（名为 `proposals.csv`），里面有你要发送邮件的人：
|
||||
|
||||
```
|
||||
firstname,lastname,email,title
|
||||
Harry,Potter,hpotter@hogwarts.edu,"Defeating your nemesis in 3 easy steps"
|
||||
Jack,Reacher,reacher@covert.mil,"Hand-to-hand combat for beginners"
|
||||
Mickey,Mouse,mmouse@disney.com,"Surviving public speaking with a squeaky voice"
|
||||
Santa,Claus,sclaus@northpole.org,"Efficient list-making"
|
||||
```
|
||||
|
||||
你要读取 CSV 文件，替换第一个文件中的相关字段（跳过第一行），然后把结果写到一个叫 `acceptanceN.txt` 的文件中，每解析一行就递增 `N`。
|
||||
|
||||
把 `awk` 程序写在一个叫 `mail_merge.awk` 的文件中。在 `awk` 脚本中的语句用 `;` 分隔。第一个任务是设置字段分隔符变量和其他几个脚本需要的变量。你还需要读取并丢弃 CSV 中的第一行，否则会创建一个以 `Dear firstname` 开头的文件。要做到这一点，请使用特殊函数 `getline`，并在读取后将记录计数器重置为 0。
|
||||
|
||||
```
|
||||
BEGIN {
|
||||
FS=",";
|
||||
template="email_template.txt";
|
||||
output="acceptance";
|
||||
getline;
|
||||
NR=0;
|
||||
}
|
||||
```
|
||||
|
||||
主要功能非常简单：每处理一行，就为各种字段设置一个变量 —— `firstname`、`lastname`、`email` 和 `title`。模板文件被逐行读取，并使用函数 `sub` 将任何出现的特殊字符序列替换为相关变量的值。然后将该行以及所做的任何替换输出到输出文件中。
|
||||
|
||||
由于每行都要处理模板文件和不同的输出文件，所以在处理下一条记录之前，需要清理和关闭这些文件的文件句柄。
|
||||
|
||||
```
|
||||
{
|
||||
# Read relevant fields from input file
|
||||
firstname=$1;
|
||||
lastname=$2;
|
||||
email=$3;
|
||||
title=$4;
|
||||
|
||||
# Set output filename
|
||||
outfile=(output NR ".txt");
|
||||
|
||||
# Read a line from template, replace special fields, and
|
||||
# print result to output file
|
||||
while ( (getline ln < template) > 0 )
|
||||
{
|
||||
sub(/{firstname}/,firstname,ln);
|
||||
sub(/{lastname}/,lastname,ln);
|
||||
sub(/{email}/,email,ln);
|
||||
sub(/{title}/,title,ln);
|
||||
print(ln) > outfile;
|
||||
}
|
||||
|
||||
# Close template and output file in advance of next record
|
||||
close(outfile);
|
||||
close(template);
|
||||
}
|
||||
```
|
||||
|
||||
你已经完成了! 在命令行上运行该脚本：
|
||||
|
||||
|
||||
```
|
||||
awk -f mail_merge.awk proposals.csv
|
||||
```
|
||||
|
||||
或
|
||||
|
||||
```
|
||||
awk -f mail_merge.awk < proposals.csv
|
||||
```
|
||||
|
||||
你会发现在当前目录下生成的文本文件。
|
||||
|
||||
### awk 进阶：字频计数
|
||||
|
||||
`awk` 中最强大的功能之一是关联数组，在大多数编程语言中，数组条目通常由数字索引，但在 `awk` 中，数组由一个键字符串进行引用。你可以从上一节的文件 `proposals.txt` 中存储一个条目。例如，在一个单一的关联数组中，像这样：
|
||||
|
||||
```
|
||||
proposer["firstname"]=$1;
|
||||
proposer["lastname"]=$2;
|
||||
proposer["email"]=$3;
|
||||
proposer["title"]=$4;
|
||||
```
|
||||
|
||||
这使得文本处理变得非常容易。一个使用了这个概念的简单的程序就是词频计数器。你可以解析一个文件，在每一行中分解出单词（忽略标点符号），对行中的每个单词进行递增计数器，然后输出文本中出现的前 20 个单词。
|
||||
|
||||
首先，在一个名为 `wordcount.awk` 的文件中，将字段分隔符设置为包含空格和标点符号的正则表达式：
|
||||
|
||||
```
|
||||
BEGIN {
|
||||
# ignore 1 or more consecutive occurrences of the characters
|
||||
# in the character group below
|
||||
FS="[ .,:;()<>{}@!\"'\t]+";
|
||||
}
|
||||
```
|
||||
|
||||
接下来，主循环函数将遍历每个字段，忽略任何空字段（如果行末有标点符号，则会出现这种情况），并递增行中单词数：
|
||||
|
||||
```
|
||||
{
|
||||
for (i = 1; i <= NF; i++) {
|
||||
if ($i != "") {
|
||||
words[$i]++;
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
最后，处理完文本后，使用 `END` 函数打印数组的内容，然后利用 `awk` 的能力，将输出的内容用管道输入 shell 命令，进行数字排序，并打印出 20 个最常出现的单词。
|
||||
|
||||
```
|
||||
END {
|
||||
sort_head = "sort -k2 -nr | head -n 20";
|
||||
for (word in words) {
|
||||
printf "%s\t%d\n", word, words[word] | sort_head;
|
||||
}
|
||||
close (sort_head);
|
||||
}
|
||||
```
|
||||
|
||||
在这篇文章的早期草稿上运行这个脚本，会产生这样的输出：
|
||||
|
||||
```
|
||||
[dneary@dhcp-49-32.bos.redhat.com]$ awk -f wordcount.awk < awk_article.txt
|
||||
the 79
|
||||
awk 41
|
||||
a 39
|
||||
and 33
|
||||
of 32
|
||||
in 27
|
||||
to 26
|
||||
is 25
|
||||
line 23
|
||||
for 23
|
||||
will 22
|
||||
file 21
|
||||
we 16
|
||||
We 15
|
||||
with 12
|
||||
which 12
|
||||
by 12
|
||||
this 11
|
||||
output 11
|
||||
function 11
|
||||
```
|
||||
|
||||
### 下一步是什么？
|
||||
|
||||
如果你想了解更多关于 `awk` 编程的知识，我强烈推荐 Dale Dougherty 和 Arnold Robbins 所著的《[Sed 和 awk][8]》这本书。
|
||||
|
||||
`awk` 编程进阶的关键之一是掌握“扩展正则表达式”。`awk` 为你可能已经熟悉的 sed [正则表达式][9]语法提供了几个强大的补充。
|
||||
|
||||
另一个学习 `awk` 的好资源是 [GNU awk 用户指南][10]。它有一个完整的 `awk` 内置函数库的参考资料，以及很多简单和复杂的 `awk` 脚本的例子。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/10/advanced-awk
|
||||
|
||||
作者：[Dave Neary][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[wxy](https://github.com/wxy)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
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|
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[a]: https://opensource.com/users/dneary
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/checklist_hands_team_collaboration.png?itok=u82QepPk (a checklist for a team)
|
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[2]: mailto:pc@event.org
|
||||
[3]: mailto:hpotter@hogwarts.edu
|
||||
[4]: mailto:reacher@covert.mil
|
||||
[5]: mailto:mmouse@disney.com
|
||||
[6]: mailto:sclaus@northpole.org
|
||||
[7]: mailto:dneary@dhcp-49-32.bos.redhat.com
|
||||
[8]: https://www.amazon.com/sed-awk-Dale-Dougherty/dp/1565922255/book
|
||||
[9]: https://en.wikibooks.org/wiki/Regular_Expressions/POSIX-Extended_Regular_Expressions
|
||||
[10]: https://www.gnu.org/software/gawk/manual/gawk.html
|
||||
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Reference in New Issue
Block a user