The awk command is mainly used in Linux for text processing, and is especially good at extracting, filtering and manipulating structured data by rows and columns. Its core uses include: 1. Extract specific column content, and divide fields with spaces or tabs by default. References such as $1, $2, etc., such as who | awk '{print $1}' can display the user name; 2. Filter row content by condition, such as awk '/error/ {print}' can find log rows containing "error", or filter specific column values through $3 == "404"; 3. Custom delimiters to process complex formats, specify input delimiters with -F parameter, such as awk -F: '{print $1, $6}' to process colon-delimited /etc/passwd files, and set output delimiters through OFS variables to beautify the results.
In Linux systems, the awk command is mainly used for text processing, especially to extract, filter and manipulate data by rows and columns. It is especially suitable for processing structured text (such as log files, CSV files, etc.), allowing you to quickly crawl key information or generate reports.
Extract specific column content
This is one of the most common uses of awk . By default, awk will split each line into multiple fields by space or tab, and you can reference them by $1 and $2 .
For example, view the username of the currently logged in user:
who | awk '{print $1}'This way, only the column of username can be displayed. You can also output multiple fields at the same time, such as:
who | awk '{print $1, $2}'You can clearly see the user name and terminal device information.
Filter row content by condition
In addition to extracting columns, awk also supports filtering logic similar to "if" statements. For example, if you want to find the line containing "error" in a log file:
awk '/error/ {print}' /var/log/syslogOr more specific, such as finding rows whose third column is equal to a certain value:
awk '$3 == "404" {print}' access.logThis writing method is very suitable for log analysis or data cleaning.
Custom separators handle complex formats
Sometimes data is not separated by spaces, but commas, colons, or other symbols. At this time, you can use the -F parameter to specify the separator.
For example, when processing /etc/passwd files, it is separated by colons:
awk -F: '{print $1, $6}' /etc/passwd This prints out the username and their home directory path. If you want to use other symbols to connect fields when output, you can set the output separator with OFS variables:
awk -F: 'BEGIN{OFS=" -> "} {print $1, $6}' /etc/passwdThis looks clearer.
Let's summarize
-
awkis suitable for processing structured text data - You can extract specific columns, filter by condition, and customize separators
- Very practical in system log analysis and data report generation
Basically all that is, it is not complicated but it is easy to ignore its power.
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