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wiki:invokingbash [2017/12/05 22:53] (current)
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 +===== Invoking a Bash Script =====
 +
 +  * Any collection of bash commands may be stored in a file; a shell script file (usually called namefile.sh ).\\
 +  * The collection of bash commands can be written and saved in a text editor (kate).\\
 +  * Bash can be invoked to execute the commands in that file by typing sh namefile.sh.\\
 +Example:
 +  - Open a text editor and write
 +<code bash>
 +echo "How many files/​folders i have in this directory?" ​
 +ls | wc -l
 +</​code>​
 +  - Save the file in the current directory as //​myfirstscript.sh//​
 +  - Run it by typing.
 +<code bash>
 +bash myfirstscript.sh
 +</​code>​
 +Of course myfirstscript.sh can include several commands and can be run recursively.\\
 +Like other programming languages bash has variables and flow control statements: e.g. if-then-else,​ while, for, goto.\\
 +Moreover it is possible to insert other scripts built up under other software languages.\\
 +
 +===== The use of arguments by invoking a Bash Script =====
 +Arguments or parameters are variables that can be inserted after "sh myfirstscript"​ and are are passed to your script.\\
 +The use of arguments has the following syntax:\\
 +//bash filename.sh argument1 argument2 argument3 ....//\\
 +and in the script the arguments are recalled as:\\
 +//argument1 = $1//\\
 +//argument2 = $2//\\
 +.....\\
 +Example:\\
 +  - Open a text editor and write:
 +<code bash>
 +echo "use $1"
 +echo "to create $2" ​
 +</​code>​
 +  - Save the file in the current directory as //​myfirstscript.sh//​
 +  - Run it by typing:
 +<code bash>
 +bash myfirstscript.sh input.txt output.txt
 +</​code>​
 +The use of arguments are very useful to create a little script that computes operation that are later recalled in other scripts. A practical example is to create a script called //​average.sh//​ that calculate the average in a column data using the input.txt file and produces the output.txt file.
  
wiki/invokingbash.txt ยท Last modified: 2017/12/05 22:53 (external edit)