New Mexico Tech
Earth and Environmental Science

ERTH 401 / GEOP 501 - Computational Methods & Tools

Lab 8: Unix I

Understanding Unix and shell scripting are very useful tools that can work alongside your developing Python knowledge. In this lab you will exercise some of the commands we discussed in lecture, gain experience with using/understanding the manual pages for other commands, and write some simple shell scripts.

1) make a new directory (~/geop501/lab08)

Copy the lab08 files into this directory and unpack them:

    $> tar xf lab08_files.tar

2) Unix command scavenger hunt (hint, use man pages!)

Use the following commands:

a) date: print out the current date and time in seconds in Epoch time (since 00:00:00 UTC Jan 1, 1970)
b) cat: put contents of file1 and file2 sequentially together into a new file file3.
c) touch: create a new file unless it already exists
d) split: break a 500-line file (largefile.txt) into multiple files that each have 50 lines
e) sort: sort a file on the first column in largefile2.txt and write only the non-repeating lines to a new file
f) uniq: print out only the non-repeating lines in the largefile2.txt

Please submit the commands and their output as a separate, well-commented deliverable (text file, for instance).

3) work with file lab8_station_list.txt.

First, using Unix tools, describe the contents of this file (what do you think it contains, how is it structured, how many lines, how many characters). Provide the commands that you use to figure this out.

a) Write down 1 line of Unix commands that allows you to view the first 20 lines of file lab8_station_list.txt (station_name latitude longitude) and pipe the output of this into another command that can count the lines and show that, indeed, we have 20 lines.

b) Write down 1 piped sequence of commands to view a sorted version of the last 10 lines of the same file. Sort by station name in column 1.

c) Write down 1 piped sequence of commands that you would use to view the 15 northern-most station in that file.

4) Reading Simple Scripts

Use the simple tcsh script below (copy it into a file lab8_script4.sh and change permissions to be executable [figure out how from past labs if you don't remember]). Add comments to each line explaining what it is doing, and provide a commented line at the end of the script that describes the output you get when running the script.

    #!/bin/tcsh
    set directory=~/geop501/lab08
    cd $directory
    pwd
    ls
    ls | wc -l
  

5) Take the script from part 4 and convert it into a working bash script called lab8_script5.sh

6) Modifying Simple Scripts

Using either bash or tcsh, write a shell script that:

• takes the name of a file from the user,
• checks whether the file exists,
• and prints out text depending on whether the file:
  • 1) exists,
  • 2) does not exist,
  • 3) exists but is empty.

In your current ~/geop501/lab08 directory check the filenames below and provide the output of your program.

lab8_station_list.txt
lab8_section6.txt
lab8_section7.txt  

7) Adding Complexity

Now copy your shell script from task 6 into a new file named lab08_script7.sh, such that it:

• takes a filename
• checks if it exists and has three columns (maybe 3 words in line 1?)
• if that's true, it calls the Python script you wrote for lab 7, exercise 5B with this file as an argument to print out the stations within the given region

You will call this as:

  $> lab08_script7.sh stations.txt

8) More Complexity

Now copy your shell script from task 7 into a new file named lab08_script8.sh and make the latitude longitude box a command line argument to both, the shell script lab08_script8.sh and the python script, such that we can call:

  $> lab08_script8.sh stations.txt 32 34 -106 -103