CentOS row counting method and efficiency test

Note: Blue = command name light green = command parameter light blue = Option purple = directory system environment: Cent

Note: Blue = command name

Light green = command parameters

Light blue = Option

Purple = Directory

System environment: CentOS 6.2 i686

I. statistics on the number of rows

1. system commands:Wc-l filename

2. grep method:Grep-c "" filename

3. sed method:Sed-n' $ = 'filename'

4. awk method:Awk 'end {print NR} 'filename

II. efficiency testing

Generate the required test File: awk 'In in {for (I = 0; I <10000000; I ++) print I} '> test

Note: the methods described in this article are used to perform three tests on the test file and calculate the time. the average value is used for comparison.

1. wc method: time wc-l test

Time:0.234 s 0.242 s 0.237 s

Average:0.237667 s

2. grep method:Time grep-c "" test

Time:1.503 s 1.340 s 1.414 s

Average:1.419000 s

3. sed method: time sed-n' $ = 'Test

Time:2.268 s 2.258 s 2.344 s

Average:2.290000 s

4. awk method: time awk 'end {print NR} 'test

Time:1.637 s 1.638 s 1.649 s

Average:1.641330 s

 

Summary:

Wc is much more efficient than other methods. efficiency: wc> grep> awk> sed

 

Supplement: wc usage

Syntax: wc [option] file

Note: this command counts the number of bytes, number of words, and number of lines in a given file. If no file name is provided, it is read from the standard input. Wc also provides the president count for all specified files. Is the largest string separated by space characters.

The options of this command are as follows:

-C: counts the number of bytes.

-L number of statistics rows.

-W counts the number of words.

These options can be used in combination

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