The "awk" command is a powerful tool for processing and manipulating data in Linux. It can perform various operations on text files, such as filtering, formatting, calculating, and reporting. In this article, you will learn how to use the "awk" command to process data in Linux, with some examples and tips.
"awk" is a programming language that was designed for text processing. It was created in the 1970s by Alfred Aho, Peter Weinberger, and Brian Kernighan, whose initials form the name "awk". "awk" can be used as a standalone command or as a script file. It has built-in features for pattern matching, variables, arrays, functions, and control structures.
Awk est un outil en ligne de commande Linux de traitement de texte et de données tabulaires utiliser pour manipuler et analyser des fichiers texte ou la sortie standard.
O comando awk é uma ferramenta poderosa para manipula??o de texto no Linux. Ele permite filtrar e processar a saída de outros programas aplicando regras com padr?es e a??es. O awk trabalha com programas que contêm regras compostas por padr?es e a??es. Um padr?o é delimitado por chaves {} e define o texto que será processado. Uma a??o é executada no texto que corresponde ao padr?o. Juntos, um padr?o e uma a??o formam uma regra. O programa awk completo é delimitado por aspas simples (').
AWK is a simple programming language for Unix and its derivatives; it excels at processing tabular data. .
To use "awk" as a command, you need to specify a program and an input file. The program consists of one or more patterns and actions, enclosed in curly braces. The syntax is: awk 'program' file For example, to print the first and third fields of each line in a file, separated by a comma, you can use: awk '{print $1","$3}' file The dollar sign ($) indicates a field number, and the comma is a literal character. You can also use regular expressions to match patterns, and arithmetic operators to perform calculations.
Imaginons que nous souhaitions n'afficher que les colonnes Filesystem(1) et Capacity(5) de la commande df dont les lignes commencent par '/dev/': df -h | awk '$0 ~ "\/dev\/" {print $1,$5}'
Suponha que queremos extrair apenas os nomes das contas de usuário a partir da saída do comando who. Podemos usar o seguinte comando: who | awk '{print $1}' Nesse exemplo: $1 representa o primeiro campo (nome de usuário). O awk imprime apenas o primeiro campo e descarta o restante da linha.
chercher les dossiers contenants le plus de fichiers : find . -type f | awk -v FS='/' '{a[$2]++}END{for (i in a) print (a[i], " ",i) | sort -n
To use "awk" as a script file, you need to write the program in a separate file, and make it executable. The file should start with a shebang line that indicates the path to the "awk" interpreter. The syntax is:
#!/usr/bin/awk -f
program
For example, to create a script file that prints the average of the second field of each line in a file, you can write:
#!/usr/bin/awk -f
BEGIN {sum = 0; count = 0}
{sum += $2; count++}
END {print sum/count}
The BEGIN and END blocks are special patterns that execute before and after the input file is processed. You can then run the script file by passing the input file as an argument: ./script file
O awk também possui fun??es internas para manipula??o de dados. Por exemplo, podemos calcular a soma de valores em um arquivo usando a fun??o sum += $1. Isso exibirá o nome de usuário e o horário de login (quarto campo).
"awk" supports both scalar and array variables. You can assign values to variables using the equal sign (=), and access them using the dollar sign ($). For example, to print the number of lines in a file, you can use: awk '{n=$0} END {print n}' file The variable n stores the value of the current line ($0), and is printed at the end. You can also use predefined variables, such as NR (number of records), NF (number of fields), and FS (field separator).
Arrays are indexed by strings or numbers, and can store multiple values. You can assign values to arrays using brackets ([]), and access them using the same syntax. For example, to print the frequency of each word in a file, you can use: awk '{for (i=1; i<=NF; i++) word[$i]++} END {for (w in word) print w, word[w]}' file The array word stores the count of each word ($i), and is printed at the end. The for loop iterates over each field and each index of the array.
"awk" supports both built-in and user-defined functions. You can call a function by using its name and passing arguments in parentheses. For example, to print the length of each line in a file, you can use: awk '{print length($0)}' file The length function returns the number of characters in a string. You can also define your own functions using the function keyword, and return values using the return keyword. For example, to create a function that reverses a string, you can write:
function reverse(s) {
r = ""
for (i=length(s); i>0; i--)
r = r substr(s,i,1)
return r
}
The function reverse takes a string s as an argument, and returns a new string r that is the reverse of s. The substr function returns a substring of a string.
Control structures are used to control the flow of execution in "awk". They include if-else, for, while, and break. For example, to print only the lines that contain the word "Linux" in a file, you can use: awk '{if ($0 ~ /Linux/) print $0}' file The if-else statement evaluates a condition and executes a block of code accordingly. The tilde (~) operator matches a regular expression.
Making the most of "awk" requires a few tips and tricks. For example, you can enclose the program in either single or double quotes, but be sure to use the appropriate escape characters. You can also use multiple input files by separating them with spaces, as well as standard input and output redirections. Additionally, you can use command-line options to modify "awk"'s behavior, such as changing the field separator to a colon. With these techniques, you can make "awk" work for you!
Imaginons que vous souhaitiez traiter un fichier au format csv dont le séparateur est le caractère ';' : awk -F ';' fichier.csv
faire un cat "lent", en pausant 1 seconde a chaque ligne affichée : cat fichier | awk '{print ; system("sleep 1")}' utilisable aussi avec une commande : find . | awk '{print ; system ("sleep 1")}'
O comando "awk" é uma ferramenta poderosa para processar dados no Linux. Ele permite manipular dados estruturados e gerar relatórios formatados. Para usar o "awk", comece identificando o arquivo de dados que você deseja processar. Em seguida, escreva um script "awk" que define como os dados devem ser processados. Isso pode incluir opera??es como impress?o de campos específicos, cálculo de somas ou médias, ou reformatar a saída. Lembre-se, a chave para usar efetivamente o "awk" é entender a estrutura dos seus dados e definir claramente o que você deseja alcan?ar.
Ce que j'ai trouvé très utile avec awk, c'est de pouvoir retirer les lignes vides d'un ou plusieurs fichiers. $ awk '1' RS='' file