updated

LDP/howto/linuxdoc/Bash-Prog-Intro-HOWTO.sgml

@@ -9,7 +9,7 @@
 <article>
     <title>BASH Programming - Introduction HOW-TO</title>
     <author>by Mike G <tt/mikkey@dynamo.com.ar/</author>
-    <date>v0.05, 20 June 2000</date>
+    <date>v0.06, 21 June 2000</date>
     <abstract> 
     This article intends to help you to start programming 
     basic-intermediate shell scripts. It does not intend to be an 
@@ -388,6 +388,23 @@ Conditionals
 	    fi
 	    </verb></tscreen>
 	</sect1>
+<!--
+	<sect1>
+	Sample: testing if a file exists 
+	    <P> one more thank to mike 
+	    <tscreen><verb>
+	    #!/bin/bash
+	    FILE=~/.basrc
+	    if [ -f $FILE ]; then
+	        echo file $FILE exits
+	    else
+	        echo file not found
+	    fi
+	    if [ 'test -f $FILE']
+	    </verb></tscreen>
+	</sect1>
+-->
+
 </sect>
 
 <!-- Loops : for, while and until -->
@@ -570,16 +587,61 @@ Misc
 	  "echo 3/4|bc -l", it would properly return 0.75.
     </sect1>
 
+
+    <sect1>
+    Finding bash  
+         <P> From a message from mike (see Thanks to) 
+         <P> you always use #!/bin/bash .. you might was to give an example of
+         <P> how to find where bash is located.
+         <P> 'locate bash' is preferred, but not all machines have locate.
+         <P> 'find ./ -name bash' from the root dir will work, usually.
+         <P> Suggested locations to check:
+         <P>         ls -l /bin/bash
+         <P>         ls -l /sbin/bash
+         <P>         ls -l /usr/local/bin/bash
+         <P>         ls -l /usr/bin/bash
+         <P>         ls -l /usr/sbin/bash
+         <P>         ls -l /usr/local/sbin/bash
+         <P> (can't think of any other dirs offhand...  i've found it in
+         <P> most of these places before on different system).
+   </sect1>
+
     <!-- Capturing a commands output  -->    
     <sect1>
-    Capturing a commands output
-         <P> __TO-DO__
+    Getting the return value of a program
+        <P> In bash, the return value of a program is stored in a special variable called $?.
+	<P> This illustrates how to capture the return value of a program, I assume that the directory
+	/dada does not exist. (This was also suggested by mike)
+	<tscreen><verb>
+	#!/bin/bash
+	cd /dada &> /dev/null
+	echo rv: $?
+	cd $(pwd) &> /dev/null
+	echo rv: $?
+	</verb> </tscreen>
+    </sect1>
+ 
+ 
+    <!-- Capturing a commands output  -->    
+    <sect1>
+    Capturing a commands output 
+         <P> This little scripts show all tables from all databases (assuming you got MySQL installed). 
+	Also, consider changing the 'mysql' command to use a valid username and password.
+	<tscreen><verb>
+	#!/bin/bash
+	DBS=`mysql -uroot  -e"show databases"`
+	for b in $DBS ;
+	do
+	        mysql -uroot -e"show tables from $b"
+	done
+	</verb></tscreen>
     </sect1>
     
     <!-- Multiple source files -->
     <sect1>
     Multiple source files
-         <P> __TO-DO__
+        <P> You can use multiple files with the command source. 
+	<P> __TO-DO__
     </sect1>
 </sect>
 
@@ -827,6 +889,9 @@ About the document
 	 <item> Jon Abbott for sending comments about evaluating arithmetic expressions.
 	 <item> Laurent Martelli for  translating this document to French (soon here the URL)
 	 <item> Felix Hudson for writing the <it/renna/ script
+
+	 <item> Mike (pink) made some suggestions about locating bash and testing files
+	 
      </itemize>
      </sect1>
 	<sect1>