Difference between revisions of "Introduction to Linux in HPC/Text display search"

From HPC Wiki
Introduction to Linux in HPC/Text display search
Jump to navigation Jump to search
Line 48: Line 48:
 
{
 
{
 
|type="()"}
 
|type="()"}
- command > filename
+
- <code>command > filename</code>
 
||  
 
||  
+ command >> filename
+
+ <code>command >> filename</code>
|| Explanation: The > operator redirects the output of command into filename. If filename exists already, its contents will be overwritten. The >> operator can redirect the output of command into filename as well, except that if filename exists, the new data are appended instead of overwritten.
+
|| Explanation: The <code>></code> operator redirects the output of command into filename. If filename exists already, its contents will be overwritten. The <code>>></code> operator can redirect the output of command into filename as well, except that if filename exists, the new data are appended instead of overwritten.
 
</quiz>
 
</quiz>
 
{{hidden end}}
 
{{hidden end}}
Line 57: Line 57:
 
{{hidden begin  
 
{{hidden begin  
 
|title = 2. How do I find all files containing specific text on Linux? </br>
 
|title = 2. How do I find all files containing specific text on Linux? </br>
HINT: use grep command
+
HINT: use <code>grep</code> command
 
}}
 
}}
 
<quiz display=simple>
 
<quiz display=simple>
Line 63: Line 63:
 
|type="()"}
 
|type="()"}
 
+ Click and submit to see the answer
 
+ Click and submit to see the answer
|| grep -rnw '/path/to/somewhere/' -e 'pattern'
+
|| <code>grep -rnw '/path/to/somewhere/' -e 'pattern'</code>
 
|| -r or -R is recursive,
 
|| -r or -R is recursive,
 
|| -n is line number, and
 
|| -n is line number, and
Line 75: Line 75:
  
 
{{Warning|mode=warn|text= '''no warnings in this section'''}}
 
{{Warning|mode=warn|text= '''no warnings in this section'''}}
 
  
 
=== Exercises in Terminal (slide 65) === <!--T:5-->   
 
=== Exercises in Terminal (slide 65) === <!--T:5-->   

Revision as of 11:44, 2 October 2020

Video

Linux Introduction Slides 58 - 64 (7 pages)


Slide Layout

   page 1: 
       grep command and syntax
       important options: -r, -i and -I
   page 2: 
       many commands to display text
       cat
       less
       head and tail
   page 3: 40 sec
       console has three streams
           stdin
           stdout
           stderr
   page 4: 
       stream in computing terms
       similar to streaming video
       input/output stream in console
   page 5: 
       input/output streams can be redirected
           redirect stdout
           redirect stdin
           pipe
   page 6: 
       stream append redirection
       numbered streams: 0 for stdin, 1 for stdout, 2 for stderr
   page 7: 
       use grep to search piped output text


Quiz

1. Which command can be used to append text to filename?

command > filename
command >> filename

2. How do I find all files containing specific text on Linux?
HINT: use grep command

Click and submit to see the answer


Info:  no tips in this section


Warning:  no warnings in this section

Exercises in Terminal (slide 65)

1. Create a file using cat (some filename) and write some text in it as below. than use grep to find and display the line number and the line with the word Alan in the file.
        the best way to predict
        the future is to invent it
        –  Alan Kay