Requirement-Driven Linux Shell ProgrammingRequirement-Driven Linux Shell Programming

requirement-driven linux shell programming

recently, i am doing a little project on linux filesystem, and some testing

work must be done by high-level applications written in c or other script

languages. when i am running the test cases, i find it annoying to do all these

works by hand, so i start to learn the linux shell programming, and i decide to

write the most important concept and skills down to remind myself or to provide

those who are interested in shell programming with the starting material…

i will record my progress and the useful skills i learned when the project is

carrying on in the q&a form, which i think is a clean and simple way to

organize my thoughts and that, i hope, won‘t take me too much time…

note:what i will cover in this post is not the step-by-step tutorial for

shell programming, but rather the kind of problems one will meet in a real

project, and i make the assumption that the readers are already equipped with

basic knowledge about the shell script.

i found this tutorial useful,a beginner‘s handbook for linux shell

scripting. there are many places you can find such materials, and you can

take a quick look at it whenever you are in need.

command format: time the_program_to_be_tested

note:the output of "time"

command will be the stderr_fileno,in my case, i want to redirect the output to a

file, so the following command is used:

<col>

time ./the_program_to_be_tested &gt; result

2&gt;&amp;1

suppose the following code section:

in this example, a function named time_xtar_load is defined, and the "for"

statement will evoke the function many times each with a different parameter,

that is, the running value of i.

the default behavior of the shell to the calculation works is limited to

integers, the tool "bc" is needed to do more advanced calculations.for example:

in the above code segment, two self-defined variables(minute, second) are

read from a file named "ctar_load_sys", they are used to get the total number in

seconds, and after the while terminates, the average time is calculated with the

last line of code.note that the "scale=10" is necessary to do the decimal

computation.

the "printf" command can do exactly what we can do in c/c++, it has rich

formats to choose from. for example:

the above code prints a table on the console as follows:

sum

avg

real

2.36

2.35

use the following command:

sed -n 1p

say, i have a file(nofs) which has the following contents:

nofs 30.049 57.857 115.718

and i want to covert it to one row, there are many ways to do it:

1.the awk way:

cat nofs

awk ‘{printf("%s ",$0)}‘

2.the tr way:

tr ‘\n‘ ‘ ‘ &lt; nofs

3.the echo:

echo $(&lt;nofs)

xargs echo &lt; nofs

cat nofs xargs

all of the above methods will output like:

tail -n +2 filename

will output the file contents from the second line.

list:

copy:

i get a file with the following format:

write rewrite read re-read randread

randwrite

32149.29 35625.84 37261.05 37575.87 713.54 1606.12

57465.48 62242.62 66024.14 66969.32 1430.75 3365.54

89339.57 96388.80 104037.65 103917.83 2714.76 6479.37

128849.01 132933.47 133952.92 134381.05 5482.03 12207.46

126489.87 128470.04 129826.87 130348.56 10446.49 24424.78

127078.48 128236.06 128642.23 129169.20 19505.88 40367.71

126942.59 125676.09 128773.13 128896.08 32061.20 63187.50

127596.32 128102.95 128516.09 129485.38 51048.20 82756.15

126424.50 127839.95 128780.78 129846.62 72924.07 97219.43

125817.65 127208.07 128134.88 129057.43 92172.60 85037.41

128768.69 129389.45 130342.52 131162.48 107949.98 100109.50

127326.84 128567.19 129666.99 129796.52 117193.84 108822.87

and i just want to remove all the empty lines of the file, the following

command can be used:

sed ‘/^$/d‘ input_file_name &gt; output_file_name

or

awk ‘$1‘ input_file_name &gt; output_file_name

the command will output the following result:

use the following script:

author: wujing

created: 2014-05-01 四 11:48

24.3.1

( mode 8.2.6)