2. Getting Started with awk

The basic function of awk is to search files for lines (or other units of text) that contain certain patterns. When a line matches one of the patterns, awk performs specified actions on that line. awk keeps processing input lines in this way until it reaches the end of the input files.

Programs in awk are different from programs in most other languages, because awk programs are data-driven; that is, you describe the data you want to work with and then what to do when you find it. Most other languages are procedural; you have to describe, in great detail, every step the program is to take. When working with procedural languages, it is usually much harder to clearly describe the data your program will process. For this reason, awk programs are often refreshingly easy to write and read.

When you run awk, you specify an awk program that tells awk what to do. The program consists of a series of rules. (It may also contain function definitions, an advanced feature that we will ignore for now. See section User-Defined Functions.) Each rule specifies one pattern to search for and one action to perform upon finding the pattern.

Syntactically, a rule consists of a pattern followed by an action. The action is enclosed in curly braces to separate it from the pattern. Newlines usually separate rules. Therefore, an awk program looks like this:

pattern { action } pattern { action } ...

2.1 How to Run awk Programs		How to run gawk programs; includes command-line syntax.
2.2 Data Files for the Examples		Sample data files for use in the awk programs illustrated in this Web page.
2.3 Some Simple Examples		A very simple example.
2.4 An Example with Two Rules		A less simple one-line example using two rules.
2.5 A More Complex Example		A more complex example.
2.6 awk Statements Versus Lines		Subdividing or combining statements into lines.
2.7 Other Features of awk
2.8 When to Use awk		When to use gawk and when to use other things.

2.1 How to Run awk Programs

There are several ways to run an awk program. If the program is short, it is easiest to include it in the command that runs awk, like this:

awk 'program' input-file1 input-file2 ...

When the program is long, it is usually more convenient to put it in a file and run it with a command like this:

awk -f program-file input-file1 input-file2 ...

This section discusses both mechanisms, along with several variations of each.

2.1.1 One-Shot Throw-Away awk Programs		Running a short throw-away awk program.
2.1.2 Running awk Without Input Files		Using no input files (input from terminal instead).
2.1.3 Running Long Programs		Putting permanent awk programs in files.
2.1.4 Executable awk Programs		Making self-contained awk programs.
2.1.5 Comments in awk Programs		Adding documentation to gawk programs.
2.1.6 Shell Quoting Issues		More discussion of shell quoting issues.

2.1.1 One-Shot Throw-Away awk Programs

Once you are familiar with awk, you will often type in simple programs the moment you want to use them. Then you can write the program as the first argument of the awk command, like this:

awk 'program' input-file1 input-file2 ...

where program consists of a series of patterns and actions, as described earlier.

This command format instructs the shell, or command interpreter, to start awk and use the program to process records in the input file(s). There are single quotes around program so the shell won't interpret any awk characters as special shell characters. The quotes also cause the shell to treat all of program as a single argument for awk, and allow program to be more than one line long.

This format is also useful for running short or medium-sized awk programs from shell scripts, because it avoids the need for a separate file for the awk program. A self-contained shell script is more reliable because there are no other files to misplace.

Some Simple Examples, later in this chapter, presents several short, self-contained programs.

2.1.2 Running awk Without Input Files

You can also run awk without any input files. If you type the following command line:

awk 'program'

awk applies the program to the standard input, which usually means whatever you type on the terminal. This continues until you indicate end-of-file by typing Ctrl-d. (On other operating systems, the end-of-file character may be different. For example, on OS/2 and MS-DOS, it is Ctrl-z.)

As an example, the following program prints a friendly piece of advice (from Douglas Adams's The Hitchhiker's Guide to the Galaxy), to keep you from worrying about the complexities of computer programming. (BEGIN is a feature we haven't discussed yet.):

$ awk "BEGIN { print \"Don't Panic!\" }" -| Don't Panic!

This program does not read any input. The `\' before each of the inner double quotes is necessary because of the shell's quoting rules--in particular because it mixes both single quotes and double quotes.(6)

This next simple awk program emulates the cat utility; it copies whatever you type at the keyboard to its standard output. (Why this works is explained shortly.)

$ awk '{ print }' Now is the time for all good men -| Now is the time for all good men to come to the aid of their country. -| to come to the aid of their country. Four score and seven years ago, ... -| Four score and seven years ago, ... What, me worry? -| What, me worry? Ctrl-d

2.1.3 Running Long Programs

Sometimes your awk programs can be very long. In this case, it is more convenient to put the program into a separate file. In order to tell awk to use that file for its program, you type:

awk -f source-file input-file1 input-file2 ...

The `-f' instructs the awk utility to get the awk program from the file source-file. Any file name can be used for source-file. For example, you could put the program:

BEGIN { print "Don't Panic!" }

into the file `advice'. Then this command:

awk -f advice

does the same thing as this one:

awk "BEGIN { print \"Don't Panic!\" }"

This was explained earlier (see section Running awk Without Input Files). Note that you don't usually need single quotes around the file name that you specify with `-f', because most file names don't contain any of the shell's special characters. Notice that in `advice', the awk program did not have single quotes around it. The quotes are only needed for programs that are provided on the awk command line.

If you want to identify your awk program files clearly as such, you can add the extension `.awk' to the file name. This doesn't affect the execution of the awk program but it does make "housekeeping" easier.

2.1.4 Executable awk Programs

Once you have learned awk, you may want to write self-contained awk scripts, using the `#!' script mechanism. You can do this on many Unix systems(7) as well as on the GNU system. For example, you could update the file `advice' to look like this:

#! /bin/awk -f BEGIN { print "Don't Panic!" }

After making this file executable (with the chmod utility), simply type `advice' at the shell and the system arranges to run awk(8) as if you had typed `awk -f advice':

$ chmod +x advice $ advice -| Don't Panic!

Self-contained awk scripts are useful when you want to write a program that users can invoke without their having to know that the program is written in awk.

Advanced Notes: Portability Issues with `#!'

Some systems limit the length of the interpreter name to 32 characters. Often, this can be dealt with by using a symbolic link.

You should not put more than one argument on the `#!' line after the path to awk. It does not work. The operating system treats the rest of the line as a single argument and passes it to awk. Doing this leads to confusing behavior--most likely a usage diagnostic of some sort from awk.

Finally, the value of ARGV[0] (see section 7.5 Built-in Variables) varies depending upon your operating system. Some systems put `awk' there, some put the full pathname of awk (such as `/bin/awk'), and some put the name of your script (`advice'). Don't rely on the value of ARGV[0] to provide your script name.

2.1.5 Comments in awk Programs

A comment is some text that is included in a program for the sake of human readers; it is not really an executable part of the program. Comments can explain what the program does and how it works. Nearly all programming languages have provisions for comments, as programs are typically hard to understand without them.

In the awk language, a comment starts with the sharp sign character (`#') and continues to the end of the line. The `#' does not have to be the first character on the line. The awk language ignores the rest of a line following a sharp sign. For example, we could have put the following into `advice':

# This program prints a nice friendly message. It helps # keep novice users from being afraid of the computer. BEGIN { print "Don't Panic!" }

You can put comment lines into keyboard-composed throw-away awk programs, but this usually isn't very useful; the purpose of a comment is to help you or another person understand the program when reading it at a later time.

Caution: As mentioned in One-Shot Throw-Away awk Programs, you can enclose small to medium programs in single quotes, in order to keep your shell scripts self-contained. When doing so, don't put an apostrophe (i.e., a single quote) into a comment (or anywhere else in your program). The shell interprets the quote as the closing quote for the entire program. As a result, usually the shell prints a message about mismatched quotes, and if awk actually runs, it will probably print strange messages about syntax errors. For example, look at the following:

$ awk '{ print "hello" } # let's be cute' >

The shell sees that the first two quotes match, and that a new quoted object begins at the end of the command-line. It therefore prompts with the secondary prompt, waiting for more input. With Unix awk, closing the quoted string produces this result:

$ awk '{ print "hello" } # let's be cute' > ' error--> awk: can't open file be error--> source line number 1

Putting a backslash before the single quote in `let's' wouldn't help, since backslashes are not special inside single quotes. The next subsection describes the shell's quoting rules.

2.1.6 Shell Quoting Issues

For short to medium length awk programs, it is most convenient to enter the program on the awk command line. This is best done by enclosing the entire program in single quotes. This is true whether you are entering the program interactively at the shell prompt, or writing it as part of a larger shell script:

awk 'program text' input-file1 input-file2 ...

Once you are working with the shell, it is helpful to have a basic knowledge of shell quoting rules. The following rules apply only to POSIX-compliant, Bourne-style shells (such as bash, the GNU Bourne-Again Shell). If you use csh, you're on your own.

• Quoted items can be concatenated with nonquoted items as well as with other quoted items. The shell turns everything into one argument for the command.

• Preceding any single character with a backslash (`\') quotes that character. The shell removes the backslash and passes the quoted character on to the command.

• Single quotes protect everything between the opening and closing quotes. The shell does no interpretation of the quoted text, passing it on verbatim to the command. It is impossible to embed a single quote inside single-quoted text. Refer back to Comments in awk Programs, for an example showing what happens if you try.

• Double quotes protect most things between the opening and closing quotes. The shell does at least variable and command substitution on the quoted text. Different shells may do additional kinds of processing on double-quoted text.

  Since certain characters within double-quoted text are processed by the shell, they must be escaped within the text. Of note are the characters `$', ``', `\' and `"', all of which must be preceded by a backslash within double-quoted text if they are to be passed on literally to the program. (The leading backslash is stripped first.) Thus, the example seen previously in Running awk Without Input Files, is applicable:

  $ awk "BEGIN { print \"Don't Panic!\" }" -| Don't Panic!

  Note that the single quote is not special within double quotes.

• Null strings are removed when they occur as part of a non-null command-line argument, while explicit non-null objects are kept. For example, to specify that the field separator FS should be set to the null string, use:

  awk -F "" 'program' files # correct

  Don't use this:

  awk -F"" 'program' files # wrong!

  In the second case, awk will attempt to use the text of the program as the value of FS, and the first file name as the text of the program! This results in syntax errors at best, and confusing behavior at worst.

Mixing single and double quotes is difficult. You have to resort to shell quoting tricks, like this:

$ awk 'BEGIN { print "Here is a single quote <'"'"'>" }' -| Here is a single quote <'>

This program consists of three concatenated quoted strings. The first and the third are single-quoted, the second is double-quoted.

This can be "simplified" to:

$ awk 'BEGIN { print "Here is a single quote <'\''>" }' -| Here is a single quote <'>

Judge for yourself which of these two is the more readable.

Another option is to use double quotes, escaping the embedded, awk-level double quotes:

$ awk "BEGIN { print \"Here is a single quote <'>\" }" -| Here is a single quote <'>

This option is also painful, because double quotes, backslashes, and dollar signs are very common in awk programs.

If you really need both single and double quotes in your awk program, it is probably best to move it into a separate file, where the shell won't be part of the picture, and you can say what you mean.

2.2 Data Files for the Examples

Many of the examples in this Web page take their input from two sample data files. The first, called `BBS-list', represents a list of computer bulletin board systems together with information about those systems. The second data file, called `inventory-shipped', contains information about monthly shipments. In both files, each line is considered to be one record.

In the file `BBS-list', each record contains the name of a computer bulletin board, its phone number, the board's baud rate(s), and a code for the number of hours it is operational. An `A' in the last column means the board operates 24 hours a day. A `B' in the last column means the board only operates on evening and weekend hours. A `C' means the board operates only on weekends:

aardvark 555-5553 1200/300 B alpo-net 555-3412 2400/1200/300 A barfly 555-7685 1200/300 A bites 555-1675 2400/1200/300 A camelot 555-0542 300 C core 555-2912 1200/300 C fooey 555-1234 2400/1200/300 B foot 555-6699 1200/300 B macfoo 555-6480 1200/300 A sdace 555-3430 2400/1200/300 A sabafoo 555-2127 1200/300 C

The second data file, called `inventory-shipped', represents information about shipments during the year. Each record contains the month, the number of green crates shipped, the number of red boxes shipped, the number of orange bags shipped, and the number of blue packages shipped, respectively. There are 16 entries, covering the 12 months of last year and the first four months of the current year.

Jan 13 25 15 115 Feb 15 32 24 226 Mar 15 24 34 228 Apr 31 52 63 420 May 16 34 29 208 Jun 31 42 75 492 Jul 24 34 67 436 Aug 15 34 47 316 Sep 13 55 37 277 Oct 29 54 68 525 Nov 20 87 82 577 Dec 17 35 61 401 Jan 21 36 64 620 Feb 26 58 80 652 Mar 24 75 70 495 Apr 21 70 74 514

If you are reading this in GNU Emacs using Info, you can copy the regions of text showing these sample files into your own test files. This way you can try out the examples shown in the remainder of this document. You do this by using the command M-x write-region to copy text from the Info file into a file for use with awk (See section `Miscellaneous File Operations' in GNU Emacs Manual, for more information). Using this information, create your own `BBS-list' and `inventory-shipped' files and practice what you learn in this Web page.

If you are using the stand-alone version of Info, see Extracting Programs from Texinfo Source Files, for an awk program that extracts these data files from `gawk.texi', the Texinfo source file for this Info file.

2.3 Some Simple Examples

The following command runs a simple awk program that searches the input file `BBS-list' for the character string `foo'. (A string of characters is usually called a string. The term string is based on similar usage in English, such as "a string of pearls," or, "a string of cars in a train."):

awk '/foo/ { print $0 }' BBS-list

When lines containing `foo' are found, they are printed because `print $0' means print the current line. (Just `print' by itself means the same thing, so we could have written that instead.)

You will notice that slashes (`/') surround the string `foo' in the awk program. The slashes indicate that `foo' is the pattern to search for. This type of pattern is called a regular expression, which is covered in more detail later (see section Regular Expressions). The pattern is allowed to match parts of words. There are single quotes around the awk program so that the shell won't interpret any of it as special shell characters.

Here is what this program prints:

$ awk '/foo/ { print $0 }' BBS-list -| fooey 555-1234 2400/1200/300 B -| foot 555-6699 1200/300 B -| macfoo 555-6480 1200/300 A -| sabafoo 555-2127 1200/300 C

In an awk rule, either the pattern or the action can be omitted, but not both. If the pattern is omitted, then the action is performed for every input line. If the action is omitted, the default action is to print all lines that match the pattern.

Thus, we could leave out the action (the print statement and the curly braces) in the above example and the result would be the same: all lines matching the pattern `foo' are printed. By comparison, omitting the print statement but retaining the curly braces makes an empty action that does nothing (i.e., no lines are printed).

Many practical awk programs are just a line or two. Following is a collection of useful, short programs to get you started. Some of these programs contain constructs that haven't been covered yet. (The description of the program will give you a good idea of what is going on, but please read the rest of the Web page to become an awk expert!) Most of the examples use a data file named `data'. This is just a placeholder; if you use these programs yourself, substitute your own file names for `data'. For future reference, note that there is often more than one way to do things in awk. At some point, you may want to look back at these examples and see if you can come up with different ways to do the same things shown here:

• Print the length of the longest input line:

  awk '{ if (length($0) > max) max = length($0) } END { print max }' data

• Print every line that is longer than 80 characters:

  awk 'length($0) > 80' data

  The sole rule has a relational expression as its pattern and it has no action--so the default action, printing the record, is used.

• Print the length of the longest line in `data':

  expand data | awk '{ if (x < length()) x = length() } END { print "maximum line length is " x }'

  The input is processed by the expand utility to change tabs into spaces, so the widths compared are actually the right-margin columns.

• Print every line that has at least one field:

  awk 'NF > 0' data

  This is an easy way to delete blank lines from a file (or rather, to create a new file similar to the old file but from which the blank lines have been removed).

• Print seven random numbers from 0 to 100, inclusive:

  awk 'BEGIN { for (i = 1; i <= 7; i++) print int(101 * rand()) }'

• Print the total number of bytes used by files:

  ls -l files | awk '{ x += $5 } END { print "total bytes: " x }'

• Print the total number of kilobytes used by files:

  ls -l files | awk '{ x += $5 } END { print "total K-bytes: " (x + 1023)/1024 }'

• Print a sorted list of the login names of all users:

  awk -F: '{ print $1 }' /etc/passwd | sort

• Count lines in a file:

  awk 'END { print NR }' data

• Print the even-numbered lines in the data file:

  awk 'NR % 2 == 0' data

  If you use the expression `NR % 2 == 1' instead, it would print the odd-numbered lines.

2.4 An Example with Two Rules

The awk utility reads the input files one line at a time. For each line, awk tries the patterns of each of the rules. If several patterns match, then several actions are run in the order in which they appear in the awk program. If no patterns match, then no actions are run.

After processing all the rules that match the line (and perhaps there are none), awk reads the next line. (However, see section The next Statement, and also see section Using gawk's nextfile Statement). This continues until the end of the file is reached. For example, the following awk program contains two rules:

/12/ { print $0 } /21/ { print $0 }

The first rule has the string `12' as the pattern and `print $0' as the action. The second rule has the string `21' as the pattern and also has `print $0' as the action. Each rule's action is enclosed in its own pair of braces.

This program prints every line that contains the string `12' or the string `21'. If a line contains both strings, it is printed twice, once by each rule.

This is what happens if we run this program on our two sample data files, `BBS-list' and `inventory-shipped', as shown here:

$ awk '/12/ { print $0 } > /21/ { print $0 }' BBS-list inventory-shipped -| aardvark 555-5553 1200/300 B -| alpo-net 555-3412 2400/1200/300 A -| barfly 555-7685 1200/300 A -| bites 555-1675 2400/1200/300 A -| core 555-2912 1200/300 C -| fooey 555-1234 2400/1200/300 B -| foot 555-6699 1200/300 B -| macfoo 555-6480 1200/300 A -| sdace 555-3430 2400/1200/300 A -| sabafoo 555-2127 1200/300 C -| sabafoo 555-2127 1200/300 C -| Jan 21 36 64 620 -| Apr 21 70 74 514

Note how the line beginning with `sabafoo' in `BBS-list' was printed twice, once for each rule.

2.5 A More Complex Example

Now that we've mastered some simple tasks, let's look at what typical awk programs do. This example shows how awk can be used to summarize, select, and rearrange the output of another utility. It uses features that haven't been covered yet, so don't worry if you don't understand all the details:

ls -l | awk '$6 == "Nov" { sum += $5 } END { print sum }'

This command prints the total number of bytes in all the files in the current directory that were last modified in November (of any year). (9) The `ls -l' part of this example is a system command that gives you a listing of the files in a directory, including each file's size and the date the file was last modified. Its output looks like this:

-rw-r--r-- 1 arnold user 1933 Nov 7 13:05 Makefile -rw-r--r-- 1 arnold user 10809 Nov 7 13:03 awk.h -rw-r--r-- 1 arnold user 983 Apr 13 12:14 awk.tab.h -rw-r--r-- 1 arnold user 31869 Jun 15 12:20 awk.y -rw-r--r-- 1 arnold user 22414 Nov 7 13:03 awk1.c -rw-r--r-- 1 arnold user 37455 Nov 7 13:03 awk2.c -rw-r--r-- 1 arnold user 27511 Dec 9 13:07 awk3.c -rw-r--r-- 1 arnold user 7989 Nov 7 13:03 awk4.c

The first field contains read-write permissions, the second field contains the number of links to the file, and the third field identifies the owner of the file. The fourth field identifies the group of the file. The fifth field contains the size of the file in bytes. The sixth, seventh and eighth fields contain the month, day, and time, respectively, that the file was last modified. Finally, the ninth field contains the name of the file.(10)

The `$6 == "Nov"' in our awk program is an expression that tests whether the sixth field of the output from `ls -l' matches the string `Nov'. Each time a line has the string `Nov' for its sixth field, the action `sum += $5' is performed. This adds the fifth field (the file's size) to the variable sum. As a result, when awk has finished reading all the input lines, sum is the total of the sizes of the files whose lines matched the pattern. (This works because awk variables are automatically initialized to zero.)

After the last line of output from ls has been processed, the END rule executes and prints the value of sum. In this example, the value of sum is 140963.

These more advanced awk techniques are covered in later sections (see section Actions). Before you can move on to more advanced awk programming, you have to know how awk interprets your input and displays your output. By manipulating fields and using print statements, you can produce some very useful and impressive looking reports.

2.6 awk Statements Versus Lines

Most often, each line in an awk program is a separate statement or separate rule, like this:

awk '/12/ { print $0 } /21/ { print $0 }' BBS-list inventory-shipped

However, gawk ignores newlines after any of the following symbols and keywords:

, { ? : || && do else

A newline at any other point is considered the end of the statement.(11)

If you would like to split a single statement into two lines at a point where a newline would terminate it, you can continue it by ending the first line with a backslash character (`\'). The backslash must be the final character on the line in order to be recognized as a continuation character. A backslash is allowed anywhere in the statement, even in the middle of a string or regular expression. For example:

awk '/This regular expression is too long, so continue it\ on the next line/ { print $1 }'

We have generally not used backslash continuation in the sample programs in this Web page. In gawk, there is no limit on the length of a line, so backslash continuation is never strictly necessary; it just makes programs more readable. For this same reason, as well as for clarity, we have kept most statements short in the sample programs presented throughout the Web page. Backslash continuation is most useful when your awk program is in a separate source file instead of entered from the command line. You should also note that many awk implementations are more particular about where you may use backslash continuation. For example, they may not allow you to split a string constant using backslash continuation. Thus, for maximum portability of your awk programs, it is best not to split your lines in the middle of a regular expression or a string.

Caution: Backslash continuation does not work as described above with the C shell. It works for awk programs in files and for one-shot programs, provided you are using a POSIX-compliant shell, such as the Unix Bourne shell or bash. But the C shell behaves differently! There, you must use two backslashes in a row, followed by a newline. Note also that when using the C shell, every newline in your awk program must be escaped with a backslash. To illustrate:

% awk 'BEGIN { \ ? print \\ ? "hello, world" \ ? }' -| hello, world

Here, the `%' and `?' are the C shell's primary and secondary prompts, analogous to the standard shell's `$' and `>'.

Compare the previous example to how it is done with a POSIX-compliant shell:

$ awk 'BEGIN { > print \ > "hello, world" > }' -| hello, world

awk is a line-oriented language. Each rule's action has to begin on the same line as the pattern. To have the pattern and action on separate lines, you must use backslash continuation; there is no other way.

Another thing to keep in mind is that backslash continuation and comments do not mix. As soon as awk sees the `#' that starts a comment, it ignores everything on the rest of the line. For example:

$ gawk 'BEGIN { print "dont panic" # a friendly \ > BEGIN rule > }' error--> gawk: cmd. line:2: BEGIN rule error--> gawk: cmd. line:2: ^ parse error

In this case, it looks like the backslash would continue the comment onto the next line. However, the backslash-newline combination is never even noticed because it is "hidden" inside the comment. Thus, the BEGIN is noted as a syntax error.

When awk statements within one rule are short, you might want to put more than one of them on a line. This is accomplished by separating the statements with a semicolon (`;'). This also applies to the rules themselves. Thus, the program shown at the start of this section could also be written this way:

/12/ { print $0 } ; /21/ { print $0 }

Note: The requirement that states that rules on the same line must be separated with a semicolon was not in the original awk language; it was added for consistency with the treatment of statements within an action.

2.7 Other Features of awk

The awk language provides a number of predefined, or built-in, variables that your programs can use to get information from awk. There are other variables your program can set as well to control how awk processes your data.

In addition, awk provides a number of built-in functions for doing common computational and string related operations. gawk provides built-in functions for working with timestamps, performing bit manipulation, and for runtime string translation.

As we develop our presentation of the awk language, we introduce most of the variables and many of the functions. They are defined systematically in 7.5 Built-in Variables, and Built-in Functions.

2.8 When to Use awk

Now that you've seen some of what awk can do, you might wonder how awk could be useful for you. By using utility programs, advanced patterns, field separators, arithmetic statements, and other selection criteria, you can produce much more complex output. The awk language is very useful for producing reports from large amounts of raw data, such as summarizing information from the output of other utility programs like ls. (See section A More Complex Example.)

Programs written with awk are usually much smaller than they would be in other languages. This makes awk programs easy to compose and use. Often, awk programs can be quickly composed at your terminal, used once, and thrown away. Because awk programs are interpreted, you can avoid the (usually lengthy) compilation part of the typical edit-compile-test-debug cycle of software development.

Complex programs have been written in awk, including a complete retargetable assembler for eight-bit microprocessors (see section Glossary, for more information), and a microcode assembler for a special purpose Prolog computer. However, awk's capabilities are strained by tasks of such complexity.

If you find yourself writing awk scripts of more than, say, a few hundred lines, you might consider using a different programming language. Emacs Lisp is a good choice if you need sophisticated string or pattern matching capabilities. The shell is also good at string and pattern matching; in addition, it allows powerful use of the system utilities. More conventional languages, such as C, C++, and Java, offer better facilities for system programming and for managing the complexity of large programs. Programs in these languages may require more lines of source code than the equivalent awk programs, but they are easier to maintain and usually run more efficiently.