Tip of the hat to Ed Morton for his help. With a single input file , it is simpler to handle line counting with a shell command in the BEGIN block , which has the following advantages:. In terms of performance, this approach is either only slightly slower than reading the file twice in awk , or even a little faster, depending on the awk implementation used:.
The following solutions deal with multiple files and make analogous assumptions :. It's not hard to generalize this to handling multiple files , but the following solution doesn't print the line count for empty files :. Things get a little trickier if you want the line count to be printed for empty files also :. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 6 years, 9 months ago.
Active 5 months ago. Viewed 8k times. I was hoping for something like the following:! Dylan Dylan 1 1 gold badge 3 3 silver badges 10 10 bronze badges. What would your desired output be if the input file is empty? Save Article. Like Article. Next cut command in Linux with examples. Recommended Articles. Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. Load Comments. Here is the same one-liner rewritten with curly braces for clarity. The 'print' statement gets executed after all the fields in the line have been replaced by their absolute values.
This one-liner matches all the lines and keeps adding the number of fields in each line. The number of fields seen so far is kept in a variable named 'total'. This one-liner has two pattern-action statements. A pattern between two slashes is a regular expression. It matches all lines containing pattern "Beth" not necessarily the word "Beth", it could as well be "Bethe" or "theBeth".
When a line matches, variable 'n' gets incremented by one. It is executed when the file has been processed. It forces '0' to be printed in case there were no matches 'n' was undefined. This one-liner keeps track of the largest number in the first field in variable 'max' and the corresponding line in variable 'maxline'. Once it has looped over all lines, it prints them out. Warning: this one-liner does not work if all the values are negative. This one-liner just prints out the predefined variable NF - Number of Fields, which contains the number of fields in the line, followed by a colon and the line itself.
Fields in Awk need not be referenced by constants. This one-liner prints the field with the value of NF. This one-liner keeps track of the last field in variable 'field'.
Once it has looped all the lines, variable 'field' contains the last field of the last line, and it just prints it out. This one-liner omits the action statement. This one-liner is similar to It references the last field by NF variable. If it's greater than 4, it prints it out. I just wrote my first e-book called " Awk One-Liners Explained ".
I improved the explanations of the one-liners in this article series, added new one-liners and added three new chapters:. Awk's default program action is to print the entire line, which is what 'print' does when invoked without parameters. This means that these three examples are the same:. This is redundant, but it does have the virtue of making the action more obvious. There's a subtle issue involved here, however. In most computer languages, strings are strings, and numbers are numbers.
There are operations that are unique to each, and one must be specifically converted to the other with conversion functions. You don't concatenate numbers, and you don't perform arithmetic operations on strings. Awk, on the other hand, makes no strong distinction between strings and numbers. In computer-science terms, it isn't a 'strongly-typed' language. All data in Awk are regarded as strings, but if that string also happens to represent a number, numeric operations can be performed on it.
So we can perform an arithmetic comparison on the date field. The first new item in this example is the END statement. To explain this, I have to extend the general form of an Awk program. The subsequent body of the Awk program consists of a series of search patterns, each with its own program action. Awk scans each line of the input file for each search pattern, and performs the appropriate actions for each string found.
Once the file has been scanned, an END clause can be used to perform any final actions required.
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