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@ -1,254 +0,0 @@
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Awk one-liners and scripts to help you sort text files)
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[#]: via: (https://opensource.com/article/19/11/how-sort-awk)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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Awk one-liners and scripts to help you sort text files
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======
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Awk is a powerful tool for doing tasks that might otherwise be left to
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other common utilities, including sort.
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![Green graph of measurements][1]
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Awk is the ubiquitous Unix command for scanning and processing text containing predictable patterns. However, because it features functions, it's also justifiably called a programming language.
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Confusingly, there is more than one awk. (Or, if you believe there can be only one, then there are several clones.) There's **awk**, the original program written by Aho, Weinberger, and Kernighan, and then there's **nawk**, **mawk**, and the GNU version, **gawk**. The GNU version of awk is a highly portable, free software version of the utility with several unique features, so this article is about GNU awk.
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While its official name is gawk, on GNU+Linux systems it's aliased to awk and serves as the default version of that command. On other systems that don't ship with GNU awk, you must install it and refer to it as gawk, rather than awk. This article uses the terms awk and gawk interchangeably.
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Being both a command and a programming language makes awk a powerful tool for tasks that might otherwise be left to **sort**, **cut**, **uniq**, and other common utilities. Luckily, there's lots of room in open source for redundancy, so if you're faced with the question of whether or not to use awk, the answer is probably a solid "maybe."
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The beauty of awk's flexibility is that if you've already committed to using awk for a task, then you can probably stay in awk no matter what comes up along the way. This includes the eternal need to sort data in a way other than the order it was delivered to you.
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### Sample set
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Before exploring awk's sorting methods, generate a sample dataset to use. Keep it simple so that you don't get distracted by edge cases and unintended complexity. This is the sample set this article uses:
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```
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Aptenodytes;forsteri;Miller,JF;1778;Emperor
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Pygoscelis;papua;Wagler;1832;Gentoo
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Eudyptula;minor;Bonaparte;1867;Little Blue
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Spheniscus;demersus;Brisson;1760;African
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Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
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Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
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Torvaldis;linux;Ewing,L;1996;Tux
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```
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It's a small dataset, but it offers a good variety of data types:
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* A genus and species name, which are associated with one another but considered separate
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* A surname, sometimes with first initials after a comma
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* An integer representing a date
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* An arbitrary term
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* All fields separated by semi-colons
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Depending on your educational background, you may consider this a 2D array or a table or just a line-delimited collection of data. How you think of it is up to you, because awk doesn't expect anything more than text. It's up to you to tell awk how you want to parse it.
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### The sort cheat
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If you just want to sort a text dataset by a specific, definable field (think of a "cell" in a spreadsheet), then you can use the [sort command][2].
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### Fields and records
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Regardless of the format of your input, you must find patterns in it so that you can focus on the parts of the data that are important to you. In this example, the data is delimited by two factors: lines and fields. Each new line represents a new _record_, as you would likely see in a spreadsheet or database dump. Within each line, there are distinct _fields_ (think of them as cells in a spreadsheet) that are separated by semicolons (;).
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Awk processes one record at a time, so while you're structuring the instructions you will give to awk, you can focus on just one line. Establish what you want to do with one line, then test it (either mentally or with awk) on the next line and a few more. You'll end up with a good hypothesis on what your awk script must do in order to provide you with the data structure you want.
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In this case, it's easy to see that each field is separated by a semicolon. For simplicity's sake, assume you want to sort the list by the very first field of each line.
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Before you can sort, you must be able to focus awk on just the first field of each line, so that's the first step. The syntax of an awk command in a terminal is **awk**, followed by relevant options, followed by your awk command, and ending with the file of data you want to process.
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```
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$ awk --field-separator=";" '{print $1;}' penguins.list
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Aptenodytes
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Pygoscelis
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Eudyptula
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Spheniscus
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Megadyptes
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Eudyptes
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Torvaldis
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```
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Because the field separator is a character that has special meaning to the Bash shell, you must enclose the semicolon in quotes or precede it with a backslash. This command is useful only to prove that you can focus on a specific field. You can try the same command using the number of another field to view the contents of another "column" of your data:
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```
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$ awk --field-separator=";" '{print $3;}' penguins.list
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Miller,JF
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Wagler
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Bonaparte
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Brisson
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Milne-Edwards
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Viellot
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Ewing,L
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```
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Nothing has been sorted yet, but this is good groundwork.
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### Scripting
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Awk is more than just a command; it's a programming language with indices and arrays and functions. That's significant because it means you can grab a list of fields you want to sort by, store the list in memory, process it, and then print the resulting data. For a complex series of actions such as this, it's easier to work in a text file, so create a new file called **sort.awk** and enter this text:
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```
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#!/bin/gawk -f
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BEGIN {
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FS=";";
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}
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```
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This establishes the file as an awk script that executes the lines contained in the file.
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The **BEGIN** statement is a special setup function provided by awk for tasks that need to occur only once. Defining the built-in variable **FS**, which stands for _field separator_ and is the same value you set in your awk command with **\--field-separator**, only needs to happen once, so it's included in the **BEGIN** statement.
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#### Arrays in awk
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You already know how to gather the values of a specific field by using the **$** notation along with the field number, but in this case, you need to store it in an array rather than print it to the terminal. This is done with an awk array. The important thing about an awk array is that it contains keys and values. Imagine an array about this article; it would look something like this: **author:"seth",title:"How to sort with awk",length:1200**. Elements like **author** and **title** and **length** are keys, with the following contents being values.
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The advantage to this in the context of sorting is that you can assign any field as the key and any record as the value, and then use the built-in awk function **asorti()** (sort by index) to sort by the key. For now, assume arbitrarily that you _only_ want to sort by the second field.
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Awk statements _not_ preceded by the special keywords **BEGIN** or **END** are loops that happen at each record. This is the part of the script that scans the data for patterns and processes it accordingly. Each time awk turns its attention to a record, statements in **{}** (unless preceded by **BEGIN** or **END**) are executed.
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To add a key and value to an array, create a variable (in this example script, I call it **ARRAY**, which isn't terribly original, but very clear) containing an array, and then assign it a key in brackets and a value with an equals sign (**=**).
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```
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{ # dump each field into an array
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ARRAY[$2] = $R;
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}
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```
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In this statement, the contents of the second field (**$2**) are used as the key term, and the current record (**$R**) is used as the value.
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### The asorti() function
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In addition to arrays, awk has several basic functions that you can use as quick and easy solutions for common tasks. One of the functions introduced in GNU awk, **asorti()**, provides the ability to sort an array by key (or _index_) or value.
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You can only sort the array once it has been populated, meaning that this action must not occur with every new record but only the final stage of your script. For this purpose, awk provides the special **END** keyword. The inverse of **BEGIN**, an **END** statement happens only once and only after all records have been scanned.
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Add this to your script:
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```
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END {
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asorti(ARRAY,SARRAY);
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# get length
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j = length(SARRAY);
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for (i = 1; i <= j; i++) {
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printf("%s %s\n", SARRAY[i],ARRAY[SARRAY[i]])
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}
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}
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```
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The **asorti()** function takes the contents of **ARRAY**, sorts it by index, and places the results in a new array called **SARRAY** (an arbitrary name I invented for this article, meaning _Sorted ARRAY_).
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Next, the variable **j** (another arbitrary name) is assigned the results of the **length()** function, which counts the number of items in **SARRAY**.
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Finally, use a **for** loop to iterate through each item in **SARRAY** using the **printf()** function to print each key, followed by the corresponding value of that key in **ARRAY**.
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### Running the script
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To run your awk script, make it executable:
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```
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`$ chmod +x sorter.awk`
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```
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And then run it against the **penguin.list** sample data:
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```
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$ ./sorter.awk penguins.list
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antipodes Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
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chrysocome Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
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demersus Spheniscus;demersus;Brisson;1760;African
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forsteri Aptenodytes;forsteri;Miller,JF;1778;Emperor
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linux Torvaldis;linux;Ewing,L;1996;Tux
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minor Eudyptula;minor;Bonaparte;1867;Little Blue
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papua Pygoscelis;papua;Wagler;1832;Gentoo
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```
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As you can see, the data is sorted by the second field.
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This is a little restrictive. It would be better to have the flexibility to choose at runtime which field you want to use as your sorting key so you could use this script on any dataset and get meaningful results.
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### Adding command options
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You can add a command variable to an awk script by using the literal value **var** in your script. Change your script so that your iterative clause uses **var** when creating your array:
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```
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{ # dump each field into an array
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ARRAY[$var] = $R;
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}
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```
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Try running the script so that it sorts by the third field by using the **-v var** option when you execute it:
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```
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$ ./sorter.awk -v var=3 penguins.list
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Bonaparte Eudyptula;minor;Bonaparte;1867;Little Blue
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Brisson Spheniscus;demersus;Brisson;1760;African
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Ewing,L Torvaldis;linux;Ewing,L;1996;Tux
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Miller,JF Aptenodytes;forsteri;Miller,JF;1778;Emperor
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Milne-Edwards Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
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Viellot Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
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Wagler Pygoscelis;papua;Wagler;1832;Gentoo
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```
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### Fixes
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This article has demonstrated how to sort data in pure GNU awk. The script can be improved so, if it's useful to you, spend some time researching [awk functions][3] on gawk's man page and customizing the script for better output.
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Here is the complete script so far:
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```
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#!/usr/bin/awk -f
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# GPLv3 appears here
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# usage: ./sorter.awk -v var=NUM FILE
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BEGIN { FS=";"; }
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{ # dump each field into an array
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ARRAY[$var] = $R;
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}
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END {
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asorti(ARRAY,SARRAY);
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# get length
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j = length(SARRAY);
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for (i = 1; i <= j; i++) {
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printf("%s %s\n", SARRAY[i],ARRAY[SARRAY[i]])
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}
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}
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```
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/19/11/how-sort-awk
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作者：[Seth Kenlon][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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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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[a]: https://opensource.com/users/seth
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/metrics_lead-steps-measure.png?itok=DG7rFZPk (Green graph of measurements)
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[2]: https://opensource.com/article/19/10/get-sorted-sort
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[3]: https://www.gnu.org/software/gawk/manual/html_node/Built_002din.html#Built_002din
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@ -0,0 +1,246 @@
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[#]: collector: (lujun9972)
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[#]: translator: (wxy)
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Awk one-liners and scripts to help you sort text files)
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[#]: via: (https://opensource.com/article/19/11/how-sort-awk)
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[#]: author: (Seth Kenlon https://opensource.com/users/seth)
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单行 Awk 或脚本帮助你排序文本文件
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======
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> Awk 是一个强大的工具，可以执行某些可能由其它常见实用程序（包括 `sort`）来完成的任务。
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![Green graph of measurements][1]
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Awk 是个普遍存在的 Unix 命令，用于扫描和处理包含可预测模式的文本。但是，由于它具有函数功能，因此也可以合理地称为编程语言。
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令人困惑的是，有不止一个 awk。（或者，如果你认为只有一个，那么其它几个就是克隆。）有 `awk`（由Aho、Weinberger 和 Kernighan 编写的原始程序），然后有 `nawk` 、`mawk` 和 GNU 版本 `gawk`。GNU 版本的 awk 是该实用程序的一个高度可移植的自由软件版本，具有几个独特的功能，因此本文是关于 GNU awk 的。
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虽然它的正式名称是 `gawk`，但在 GNU+Linux 系统上，它的别名是 `awk`，并用作该命令的默认版本。 在其他没有带有 GNU awk 的系统上，你必须安装它并将其称为 `gawk`，而不是 `awk`。本文互换使用术语 `awk` 和 `gawk`。
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`awk` 既是命令语言又是编程语言，它使其成为一个强大的工具，可以处理原本留给 `sort`、`cut`、`uniq` 和其他常见实用程序的任务。幸运的是，开放源代码中有很多冗余空间，因此，如果你面临是否使用`awk` 的问题，答案可能是肯定的“也许”。
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`awk` 的灵活之美在于，如果你已经承诺使用 `awk` 来完成一项任务，那么无论接下来发生什么，你都可以继续使用 `awk`。这包括对数据排序而不是按交付给你的顺序的永恒需求。
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### 样本数据集
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在探索 `awk` 的排序方法之前，请生成要使用的样本数据集。保持简单，这样你就不会为极端情况和意想不到的复杂性所困扰。这是本文使用的样本集：
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```
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Aptenodytes;forsteri;Miller,JF;1778;Emperor
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Pygoscelis;papua;Wagler;1832;Gentoo
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Eudyptula;minor;Bonaparte;1867;Little Blue
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Spheniscus;demersus;Brisson;1760;African
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Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
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Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
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Torvaldis;linux;Ewing,L;1996;Tux
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```
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这是一个很小的数据集，但它提供了多种数据类型：
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* 属名和种名，彼此相关但又是分开的
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* 姓，有时以逗号开头的首字母缩写
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* 代表日期的整数
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* 任意术语
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* 所有字段均以分号分隔
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根据你的教育背景，你可能会认为这是二维数组或表格，或者只是行分隔的数据集合。你如何看待它取决于你，因为 `awk` 只认识文本。由你决定告诉 `awk` 你想如何解析它。
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### 只想排序
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如果你只想按特定的可定义字段（例如电子表格中的“单元格”）对文本数据集进行排序，则可以使用 [sort 命令][2]。
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### 字段和记录
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字段和记录
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无论输入的格式如何，都必须在其中找到模式才可以专注于对你重要的数据部分。在此示例中，数据由两个因素定界：行和字段。每行都代表一个新的*记录*，就如你在电子表格或数据库转储中看到的一样。在每一行中，都有用分号（`;`）分隔的不同的*字段*（将其视为电子表格中的单元格）。
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`awk` 一次只处理一条记录，因此，当你在组织发给 `awk` 的这指令时，你可以只关注一行记录。写下你想对一行数据执行的操作，然后在下一行进行测试（无论是心理上还是用 `awk` 进行测试），然后再进行其他一些测试。最后，你要对你的 `awk` 脚本要处理的数据做好假设，以便可以按你要的数据结构提供给你数据。
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在这个例子中，很容易看到每个字段都用分号隔开。为简单起见，假设你要按每行的第一字段对列表进行排序。
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在进行排序之前，你必须能够让 `awk` 只关注在每行的第一个字段上，因此这是第一步。终端中 awk 命令的语法为 `awk'，后跟相关选项，后跟你的 `awk` 命令，最后是要处理的数据文件。
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```
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$ awk --field-separator=";" '{print $1;}' penguins.list
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Aptenodytes
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Pygoscelis
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Eudyptula
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Spheniscus
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Megadyptes
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Eudyptes
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Torvaldis
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```
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因为字段分隔符是对 Bash shell 具有特殊含义的字符，所以必须将分号括在引号中或在其前面加上反斜杠。此命令仅用于证明你可以专注于特定字段。你可以使用另一个字段的编号尝试相同的命令，以查看数据的另一个“列”的内容：
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```
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$ awk --field-separator=";" '{print $3;}' penguins.list
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Miller,JF
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Wagler
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Bonaparte
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Brisson
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Milne-Edwards
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Viellot
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Ewing,L
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```
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我们尚未进行任何排序，但这是良好的基础。
|
||||
|
||||
### 脚本编程
|
||||
|
||||
`awk` 不仅仅是命令，它是一种具有索引、数组和函数的编程语言。这很重要，因为这意味着你可以获取要排序的字段列表，将列表存储在内存中，进行处理，然后打印结果数据。对于诸如此类的一系列复杂操作，在文本文件中进行操作会更容易，因此请创建一个名为 `sort.awk` 的新文件并输入以下文本：
|
||||
|
||||
|
||||
```
|
||||
#!/bin/gawk -f
|
||||
|
||||
BEGIN {
|
||||
FS=";";
|
||||
}
|
||||
```
|
||||
|
||||
这会将文件建立为 `awk` 脚本，该脚本中包含执行的行。
|
||||
|
||||
`BEGIN` 语句是 `awk` 提供的特殊设置功能，用于只需要执行一次的任务。定义内置变量 `FS`，它代表<ruby>字段分隔符<rt>field separator</rt></ruby>，并且与你在 `awk` 命令中使用 `--field-separator` 设置的值相同，它只需执行一次，因此它包含在 `BEGIN` 语句中。
|
||||
|
||||
#### awk 中的数组
|
||||
|
||||
你已经知道如何通过使用 `$` 符号和字段编号来收集特定字段的值，但是在这种情况下，你需要将其存储在数组中而不是将其打印到终端。这是通过 `awk` 数组完成的。`awk` 数组的重要之处在于它包含键和值。 想象一下有关本文的内容；它看起来像这样：`author:"seth",title:"How to sort with awk",length:1200`。诸如作者、标题和长度之类的元素是键，跟着的内容为值。
|
||||
|
||||
在排序的上下文中这样做的好处是，你可以将任何字段分配为键，将任何记录分配为值，然后使用内置的 `awk` 函数 `asorti()`（按索引排序）按键进行排序。现在，随便假设你*只*想按第二个字段排序。
|
||||
|
||||
*没有*被特殊关键字 `BEGIN` 或 `END` 引起来的 `awk` 语句是在每个记录都有执行的循环。这是脚本的一部分，该脚本扫描数据中的模式并进行相应的处理。每次 `awk` 将注意力转移到一条记录上时，都会执行 `{}` 中的语句（除非以 `BEGIN` 或 `END` 开头）。
|
||||
|
||||
要将键和值添加到数组，请创建一个包含数组的变量（在本示例脚本中，我将其称为 `ARRAY `，虽然不是很原汁原味，但很清楚），然后在方括号中分配给它键和用等号（`=`）连接的值。
|
||||
|
||||
```
|
||||
{ # dump each field into an array
|
||||
ARRAY[$2] = $R;
|
||||
}
|
||||
```
|
||||
|
||||
在此语句中，第二个字段的内容（`$2`）用作关键字，而当前记录（`$R`）用作值。
|
||||
|
||||
|
||||
### asorti() 函数
|
||||
|
||||
除了数组之外，`awk` 还具有一些基本函数，你可以将它们用作常见任务的快速简便的解决方案。GNU awk中引入的函数之一 `asorti()` 提供了按键（*索引*）或值对数组进行排序的功能。
|
||||
|
||||
你只能在对数组进行填充后对其进行排序，这意味着此操作不能对每个新记录都触发，而只能在脚本的最后阶段进行。为此，`awk` 提供了特殊的 `END` 关键字。与 `BEGIN` 相反，`END` 语句仅在扫描了所有记录之后才触发一次。
|
||||
|
||||
将这些添加到你的脚本：
|
||||
|
||||
```
|
||||
END {
|
||||
asorti(ARRAY,SARRAY);
|
||||
# get length
|
||||
j = length(SARRAY);
|
||||
|
||||
for (i = 1; i <= j; i++) {
|
||||
printf("%s %s\n", SARRAY[i],ARRAY[SARRAY[i]])
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
`asorti()` 函数获取 `ARRAY` 的内容，按索引对其进行排序，然后将结果放入名为 `SARRAY` 的新数组（我在本文中发明的任意名称，表示“排序的 ARRAY”）。
|
||||
|
||||
接下来，将变量 `j`（另一个任意名称）分配给 `length()` 函数的结果，该函数计算 `SARRAY` 中的项数。
|
||||
|
||||
最后，使用 `for` 循环使用 `printf()` 函数遍历 `SARRAY` 中的每一项，以打印每个键，然后在 `ARRAY` 中打印该键的相应值。
|
||||
|
||||
### 运行该脚本
|
||||
|
||||
要运行你的 `awk` 脚本，先使其可执行：
|
||||
|
||||
```
|
||||
$ chmod +x sorter.awk
|
||||
```
|
||||
|
||||
然后针对 `penguin.list` 示例数据运行它：
|
||||
|
||||
```
|
||||
$ ./sorter.awk penguins.list
|
||||
antipodes Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
|
||||
chrysocome Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
|
||||
demersus Spheniscus;demersus;Brisson;1760;African
|
||||
forsteri Aptenodytes;forsteri;Miller,JF;1778;Emperor
|
||||
linux Torvaldis;linux;Ewing,L;1996;Tux
|
||||
minor Eudyptula;minor;Bonaparte;1867;Little Blue
|
||||
papua Pygoscelis;papua;Wagler;1832;Gentoo
|
||||
```
|
||||
|
||||
如你所见，数据按第二个字段排序。
|
||||
|
||||
这有点限制性。最好可以在运行时灵活选择要用作排序键的字段，以便可以在任何数据集上使用此脚本并获得有意义的结果。
|
||||
|
||||
### 添加命令选项
|
||||
|
||||
你可以通过在脚本中使用文字值 `var` 将命令变量添加到 `awk` 脚本中。更改脚本，以使迭代子句在创建数组时使用 `var`：
|
||||
|
||||
```
|
||||
{ # dump each field into an array
|
||||
ARRAY[$var] = $R;
|
||||
}
|
||||
```
|
||||
|
||||
尝试运行脚本，以便在执行脚本时使用 `-v var` 选项将其按第三字段排序：
|
||||
|
||||
```
|
||||
$ ./sorter.awk -v var=3 penguins.list
|
||||
Bonaparte Eudyptula;minor;Bonaparte;1867;Little Blue
|
||||
Brisson Spheniscus;demersus;Brisson;1760;African
|
||||
Ewing,L Torvaldis;linux;Ewing,L;1996;Tux
|
||||
Miller,JF Aptenodytes;forsteri;Miller,JF;1778;Emperor
|
||||
Milne-Edwards Megadyptes;antipodes;Milne-Edwards;1880;Yellow-eyed
|
||||
Viellot Eudyptes;chrysocome;Viellot;1816;Sothern Rockhopper
|
||||
Wagler Pygoscelis;papua;Wagler;1832;Gentoo
|
||||
```
|
||||
|
||||
### 修正
|
||||
|
||||
本文演示了如何在纯 GNU awk 中对数据进行排序。你可以对脚本进行改进，以便对你有用，花一些时间在`gawk` 的手册页上研究 [awk 函数][3]并自定义脚本以获得更好的输出。
|
||||
|
||||
这是到目前为止的完整脚本：
|
||||
|
||||
```
|
||||
#!/usr/bin/awk -f
|
||||
# GPLv3 appears here
|
||||
# usage: ./sorter.awk -v var=NUM FILE
|
||||
|
||||
BEGIN { FS=";"; }
|
||||
|
||||
{ # dump each field into an array
|
||||
ARRAY[$var] = $R;
|
||||
}
|
||||
|
||||
END {
|
||||
asorti(ARRAY,SARRAY);
|
||||
# get length
|
||||
j = length(SARRAY);
|
||||
|
||||
for (i = 1; i <= j; i++) {
|
||||
printf("%s %s\n", SARRAY[i],ARRAY[SARRAY[i]])
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: https://opensource.com/article/19/11/how-sort-awk
|
||||
|
||||
作者：[Seth Kenlon][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
|
||||
|
||||
[a]: https://opensource.com/users/seth
|
||||
[b]: https://github.com/lujun9972
|
||||
[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/metrics_lead-steps-measure.png?itok=DG7rFZPk (Green graph of measurements)
|
||||
[2]: https://opensource.com/article/19/10/get-sorted-sort
|
||||
[3]: https://www.gnu.org/software/gawk/manual/html_node/Built_002din.html#Built_002din
|
||||
Loading…
Reference in New Issue
Block a user