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diff --git a/zh-cn/awk-cn.html.markdown b/zh-cn/awk-cn.html.markdown index fcd17b4f..1fafa559 100644 --- a/zh-cn/awk-cn.html.markdown +++ b/zh-cn/awk-cn.html.markdown @@ -8,41 +8,35 @@ filename: learnawk-cn.awk lang: zh-cn --- -AWK is a standard tool on every POSIX-compliant UNIX system. It's like a -stripped-down Perl, perfect for text-processing tasks and other scripting -needs. It has a C-like syntax, but without semicolons, manual memory -management, or static typing. It excels at text processing. You can call to it -from a shell script, or you can use it as a stand-alone scripting language. - -Why use AWK instead of Perl? Mostly because AWK is part of UNIX. You can always -count on it, whereas Perl's future is in question. AWK is also easier to read -than Perl. For simple text-processing scripts, particularly ones that read -files line by line and split on delimiters, AWK is probably the right tool for -the job. +AWK是POSIX兼容的UNIX系统中的标准工具. 它像简化版的Perl, 非常适用于文本处理任务和其他脚本类需求. +它有着C风格的语法, 但是没有分号, 没有手动内存管理, 没有静态类型. +他擅长于文本处理, 你可以通过shell脚本调用AWK, 也可以用作独立的脚本语言. + +为什么使用AWK而不是Perl, 大概是因为AWK是UNIX的一部分, 你总能依靠它, 而Perl已经前途未卜了. +AWK比Perl更易读. 对于简单的文本处理脚本, 特别是按行读取文件, 按分隔符分隔处理, AWK极可能是正确的工具. ```awk #!/usr/bin/awk -f -# Comments are like this +# 注释使用井号 -# AWK programs consist of a collection of patterns and actions. The most -# important pattern is called BEGIN. Actions go into brace blocks. +# AWK程序由一系列 模式(patterns) 和 动作(actions) 组成. +# 最重要的模式叫做 BEGIN. 动作由大括号包围. BEGIN { - # BEGIN will run at the beginning of the program. It's where you put all - # the preliminary set-up code, before you process any text files. If you - # have no text files, then think of BEGIN as the main entry point. + # BEGIN在程序最开始运行. 在这里放一些在真正处理文件之前的准备和setup的代码. + # 如果没有文本文件要处理, 那就把BEGIN作为程序的主入口吧. - # Variables are global. Just set them or use them, no need to declare.. + # 变量是全局的. 直接赋值使用即可, 无需声明. count = 0 - # Operators just like in C and friends + # 运算符和C语言系一样 a = count + 1 b = count - 1 c = count * 1 - d = count / 1 # integer division - e = count % 1 # modulus - f = count ^ 1 # exponentiation + d = count / 1 # 整数除法 + e = count % 1 # 取余 + f = count ^ 1 # 取幂 a += 1 b -= 1 @@ -51,26 +45,26 @@ BEGIN { e %= 1 f ^= 1 - # Incrementing and decrementing by one + # 自增1, 自减1 a++ b-- - # As a prefix operator, it returns the incremented value + # 前置运算, 返回增加之后的值 ++a --b - # Notice, also, no punctuation such as semicolons to terminate statements + # 注意, 不需要分号之类的标点来分隔语句 - # Control statements + # 控制语句 if (count == 0) print "Starting with count of 0" else print "Huh?" - # Or you could use the ternary operator + # 或者三目运算符 print (count == 0) ? "Starting with count of 0" : "Huh?" - # Blocks consisting of multiple lines use braces + # 多行的代码块用大括号包围 while (a < 10) { print "String concatenation is done" " with a series" " of" " space-separated strings" @@ -82,126 +76,118 @@ BEGIN { for (i = 0; i < 10; i++) print "Good ol' for loop" - # As for comparisons, they're the standards: - a < b # Less than - a <= b # Less than or equal - a != b # Not equal - a == b # Equal - a > b # Greater than - a >= b # Greater than or equal + # 标准的比较运算符 + a < b # 小于 + a <= b # 小于或等于 + a != b # 不等于 + a == b # 等于 + a > b # 大于 + a >= b # 大于或等于 - # Logical operators as well - a && b # AND - a || b # OR + # 也有逻辑运算符 + a && b # 且 + a || b # 或 - # In addition, there's the super useful regular expression match + # 并且有超实用的正则表达式匹配 if ("foo" ~ "^fo+$") print "Fooey!" if ("boo" !~ "^fo+$") print "Boo!" - # Arrays + # 数组 arr[0] = "foo" arr[1] = "bar" - # Unfortunately, there is no other way to initialize an array. Ya just - # gotta chug through every value line by line like that. + # 不幸的是, 没有其他方式初始化数组. 必须像这样一行一行的赋值. - # You also have associative arrays + # 关联数组, 类似map或dict的用法. assoc["foo"] = "bar" assoc["bar"] = "baz" - # And multi-dimensional arrays, with some limitations I won't mention here + # 多维数组. 但是有一些局限性这里不提了. multidim[0,0] = "foo" multidim[0,1] = "bar" multidim[1,0] = "baz" multidim[1,1] = "boo" - # You can test for array membership + # 可以检测数组包含关系 if ("foo" in assoc) print "Fooey!" - # You can also use the 'in' operator to traverse the keys of an array + # 可以使用in遍历数组 for (key in assoc) print assoc[key] - # The command line is in a special array called ARGV + # 命令行参数是一个叫ARGV的数组 for (argnum in ARGV) print ARGV[argnum] - # You can remove elements of an array - # This is particularly useful to prevent AWK from assuming the arguments - # are files for it to process + # 可以从数组中移除元素 + # 在 防止awk把文件参数当做数据来处理 时delete功能很有用. delete ARGV[1] - # The number of command line arguments is in a variable called ARGC + # 命令行参数的个数是一个叫ARGC的变量 print ARGC - # AWK has several built-in functions. They fall into three categories. I'll - # demonstrate each of them in their own functions, defined later. + # AWK有很多内置函数, 分为三类, 会在接下来定义的各个函数中介绍. return_value = arithmetic_functions(a, b, c) string_functions() io_functions() } -# Here's how you define a function +# 定义函数 function arithmetic_functions(a, b, c, d) { - # Probably the most annoying part of AWK is that there are no local - # variables. Everything is global. For short scripts, this is fine, even - # useful, but for longer scripts, this can be a problem. + # 或许AWK最让人恼火的地方是没有局部变量, 所有东西都是全局的, + # 对于短的脚本还好, 对于长一些的就会成问题. - # There is a work-around (ahem, hack). Function arguments are local to the - # function, and AWK allows you to define more function arguments than it - # needs. So just stick local variable in the function declaration, like I - # did above. As a convention, stick in some extra whitespace to distinguish - # between actual function parameters and local variables. In this example, - # a, b, and c are actual parameters, while d is merely a local variable. + # 这里有一个技巧, 函数参数是对函数局部可见的, 并且AWK允许定义多余的参数, + # 因此可以像上面那样把局部变量插入到函数声明中. + # 为了方便区分普通参数(a,b,c)和局部变量(d), 可以多键入一些空格. - # Now, to demonstrate the arithmetic functions + # 现在介绍数学类函数 - # Most AWK implementations have some standard trig functions + # 多数AWK实现中包含标准的三角函数 localvar = sin(a) localvar = cos(a) localvar = atan2(a, b) # arc tangent of b / a - # And logarithmic stuff + # 对数 localvar = exp(a) localvar = log(a) - # Square root + # 平方根 localvar = sqrt(a) - # Truncate floating point to integer + # 浮点型转为整型 localvar = int(5.34) # localvar => 5 - # Random numbers - srand() # Supply a seed as an argument. By default, it uses the time of day - localvar = rand() # Random number between 0 and 1. + # 随机数 + srand() # 接受随机种子作为参数, 默认使用当天的时间 + localvar = rand() # 0到1之间随机 - # Here's how to return a value + # 函数返回 return localvar } function string_functions( localvar, arr) { - # AWK, being a string-processing language, has several string-related - # functions, many of which rely heavily on regular expressions. + # AWK, 作为字符处理语言, 有很多字符串相关函数, 其中大多数都严重依赖正则表达式. - # Search and replace, first instance (sub) or all instances (gsub) - # Both return number of matches replaced + # 搜索并替换, 第一个出现的 (sub) or 所有的 (gsub) + # 都是返回替换的个数 localvar = "fooooobar" sub("fo+", "Meet me at the ", localvar) # localvar => "Meet me at the bar" gsub("e+", ".", localvar) # localvar => "m..t m. at th. bar" - # Search for a string that matches a regular expression - # index() does the same thing, but doesn't allow a regular expression - match(localvar, "t") # => 4, since the 't' is the fourth character + # 搜索匹配正则的字符串 + # index() 也是搜索, 不支持正则 + match(localvar, "t") # => 4, 't'在4号位置. (译者注: awk是1开始计数的,不是常见的0-base) - # Split on a delimiter + # 按分隔符分隔 split("foo-bar-baz", arr, "-") # a => ["foo", "bar", "baz"] - # Other useful stuff + # 其他有用的函数 sprintf("%s %d %d %d", "Testing", 1, 2, 3) # => "Testing 1 2 3" substr("foobar", 2, 3) # => "oob" substr("foobar", 4) # => "bar" @@ -212,99 +198,81 @@ function string_functions( localvar, arr) { function io_functions( localvar) { - # You've already seen print + # 你已经见过的print函数 print "Hello world" - # There's also printf + # 也有printf printf("%s %d %d %d\n", "Testing", 1, 2, 3) - # AWK doesn't have file handles, per se. It will automatically open a file - # handle for you when you use something that needs one. The string you used - # for this can be treated as a file handle, for purposes of I/O. This makes - # it feel sort of like shell scripting: - + # AWK本身没有文件句柄, 当你使用需要文件的东西时会自动打开文件, 做文件I/O时, 字符串就是打开的文件句柄. + # 这看起来像Shell print "foobar" >"/tmp/foobar.txt" - # Now the string "/tmp/foobar.txt" is a file handle. You can close it: + # 现在"/tmp/foobar.txt"字符串是一个文件句柄, 你可以关闭它 close("/tmp/foobar.txt") - # Here's how you run something in the shell + # 在shell里运行一些东西 system("echo foobar") # => prints foobar - # Reads a line from standard input and stores in localvar + # 从标准输入中读一行, 并存储在localvar中 getline localvar - # Reads a line from a pipe + # 从管道中读一行, 并存储在localvar中 "echo foobar" | getline localvar # localvar => "foobar" close("echo foobar") - # Reads a line from a file and stores in localvar + # 从文件中读一行, 并存储在localvar中 getline localvar <"/tmp/foobar.txt" close("/tmp/foobar.txt") } -# As I said at the beginning, AWK programs consist of a collection of patterns -# and actions. You've already seen the all-important BEGIN pattern. Other -# patterns are used only if you're processing lines from files or standard -# input. -# -# When you pass arguments to AWK, they are treated as file names to process. -# It will process them all, in order. Think of it like an implicit for loop, -# iterating over the lines in these files. these patterns and actions are like -# switch statements inside the loop. +# 正如开头所说, AWK程序由一系列模式和动作组成. 你已经看见了重要的BEGIN pattern, +# 其他的pattern在你需要处理来自文件或标准输入的的数据行时才用到. +# +# 当你给AWK程序传参数时, 他们会被视为要处理文件的文件名, 按顺序全部会处理. +# 可以把这个过程看做一个隐式的循环, 遍历这些文件中的所有行. +# 然后这些模式和动作就是这个循环里的switch语句一样 /^fo+bar$/ { - # This action will execute for every line that matches the regular - # expression, /^fo+bar$/, and will be skipped for any line that fails to - # match it. Let's just print the line: - + # 这个动作会在匹配这个正则(/^fo+bar$/)的每一行上执行. 不匹配的则会跳过. + # 先让我们打印它: print - # Whoa, no argument! That's because print has a default argument: $0. - # $0 is the name of the current line being processed. It is created - # automatically for you. + # 哦, 没有参数, 那是因为print有一个默认参数 $0. + # $0 是当前正在处理的行, 自动被创建好了. - # You can probably guess there are other $ variables. Every line is - # implicitly split before every action is called, much like the shell - # does. And, like the shell, each field can be access with a dollar sign + # 你可能猜到有其他的$变量了. + # 每一行在动作执行前会被分隔符分隔. 像shell中一样, 每个字段都可以用$符访问 - # This will print the second and fourth fields in the line + # 这个会打印这行的第2和第4个字段 print $2, $4 - # AWK automatically defines many other variables to help you inspect and - # process each line. The most important one is NF - - # Prints the number of fields on this line + # AWK自动定义了许多其他的变量帮助你处理行. 最常用的是NF变量 + # 打印这一行的字段数 print NF - # Print the last field on this line + # 打印这一行的最后一个字段 print $NF } -# Every pattern is actually a true/false test. The regular expression in the -# last pattern is also a true/false test, but part of it was hidden. If you -# don't give it a string to test, it will assume $0, the line that it's -# currently processing. Thus, the complete version of it is this: +# 每一个模式其实是一个true/false判断, 上面那个正则其实也是一个true/false判断, 只不过被部分省略了. +# 没有指定时默认使用当前处理的整行($0)进行匹配. 因此, 完全版本是这样: $0 ~ /^fo+bar$/ { print "Equivalent to the last pattern" } a > 0 { - # This will execute once for each line, as long as a is positive + # 只要a是整数, 这块会在每一行上执行. } -# You get the idea. Processing text files, reading in a line at a time, and -# doing something with it, particularly splitting on a delimiter, is so common -# in UNIX that AWK is a scripting language that does all of it for you, without -# you needing to ask. All you have to do is write the patterns and actions -# based on what you expect of the input, and what you want to do with it. +# 就是这样, 处理文本文件, 一次读一行, 对行做一些操作. 按分隔符分隔, 这在UNIX中很常见, awk都帮你做好了. +# 你所需要做的是基于自己的需求写一些模式和动作. -# Here's a quick example of a simple script, the sort of thing AWK is perfect -# for. It will read a name from standard input and then will print the average -# age of everyone with that first name. Let's say you supply as an argument the -# name of a this data file: +# 这里有一个快速的例子, 展示了AWK所擅长做的事. +# 它从标准输入读一个名字, 打印这个first name下所有人的平均年龄. +# 示例数据: # # Bob Jones 32 # Jane Doe 22 @@ -312,41 +280,36 @@ a > 0 { # Bob Smith 29 # Bob Barker 72 # -# Here's the script: +# 示例脚本: BEGIN { - # First, ask the user for the name + # 首先, 问用户要一个名字 print "What name would you like the average age for?" - # Get a line from standard input, not from files on the command line + # 从标准输入获取名字 getline name <"/dev/stdin" } -# Now, match every line whose first field is the given name +# 然后, 用给定的名字匹配每一行的第一个字段. $1 == name { - # Inside here, we have access to a number of useful variables, already - # pre-loaded for us: - # $0 is the entire line - # $3 is the third field, the age, which is what we're interested in here - # NF is the number of fields, which should be 3 - # NR is the number of records (lines) seen so far - # FILENAME is the name of the file being processed - # FS is the field separator being used, which is " " here - # ...etc. There are plenty more, documented in the man page. - - # Keep track of a running total and how many lines matched + # 这里我们要使用几个有用的变量, 已经提前为我们加载好的: + # $0 是整行 + # $3 是第三个字段, 就是我们所感兴趣的年龄 + # NF 字段数, 这里是3 + # NR 至此为止的行数 + # FILENAME 在处理的文件名 + # FS 在使用的字段分隔符, 这里是空格" " + # ...等等, 还有很多, 在帮助文档中列出. + + # 跟踪 总和以及行数 sum += $3 nlines++ } -# Another special pattern is called END. It will run after processing all the -# text files. Unlike BEGIN, it will only run if you've given it input to -# process. It will run after all the files have been read and processed -# according to the rules and actions you've provided. The purpose of it is -# usually to output some kind of final report, or do something with the -# aggregate of the data you've accumulated over the course of the script. +# 另一个特殊的模式叫END. 它会在处理完所有行之后运行. 不像BEGIN, 它只会在有输入的时候运行. +# 它在所有文件依据给定的模式和动作处理完后运行, 目的通常是输出一些最终报告, 做一些数据聚合操作. END { if (nlines) @@ -354,8 +317,8 @@ END { } ``` -Further Reading: +更多: -* [Awk tutorial](http://www.grymoire.com/Unix/Awk.html) -* [Awk man page](https://linux.die.net/man/1/awk) -* [The GNU Awk User's Guide](https://www.gnu.org/software/gawk/manual/gawk.html) GNU Awk is found on most Linux systems. +* [Awk 教程](http://www.grymoire.com/Unix/Awk.html) +* [Awk 手册](https://linux.die.net/man/1/awk) +* [The GNU Awk 用户指南](https://www.gnu.org/software/gawk/manual/gawk.html) GNU Awk在大多数Linux中预装 |