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4 Reading Input Files ¶

In the typical awk program, awk reads all input either from the standard input (by default, this is the keyboard, but often it is a pipe from another command) or from files whose names you specify on the awk command line. If you specify input files, awk reads them in order, processing all the data from one before going on to the next. The name of the current input file can be found in the predefined variable FILENAME (see Predefined Variables).

The input is read in units called records, and is processed by the rules of your program one record at a time. By default, each record is one line. Each record is automatically split into chunks called fields. This makes it more convenient for programs to work on the parts of a record.

On rare occasions, you may need to use the getline function. The getline function is valuable both because it can do explicit input from any number of files, and because the files used with it do not have to be named on the awk command line (see Explicit Input with getline).

• How Input Is Split into Records
• Examining Fields
• Nonconstant Field Numbers
• Changing the Contents of a Field
• Specifying How Fields Are Separated
• Reading Fixed-Width Data
• Defining Fields by Content
• Checking How gawk Is Splitting Records
• Multiple-Line Records
• Explicit Input with getline
• Reading Input with a Timeout
• Retrying Reads After Certain Input Errors
• Directories on the Command Line
• Summary
• Exercises