Bash: Difference between revisions

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 <source lang="bash">
 for i in `seq 1 10`; do echo "$i, "; done
+</source>
+== If construct ==
+The <code>then</code> can go on the same line as the <code>if</code> as long as you use a semi-colon to terminate the if clause.  Alternately, you can put the <code>then</code> on it's own line
+<source lang="bash">
+if EXPR; then
+  # do stuff
+fi
+</source>
+is equivalent to
+<source lang="bash">
+if EXPR
+then
+  # do stuff
+fi
+</source>
+Adding an <code>else</code> clause
+<source lang="bash">
+if EXPR; then
+  # do stuff
+else
+  # do other stuff
+fi
+</source>
+Adding multiple <code>else</code> clauses with <code>elif; then</code>
+<source lang="bash">
+if EXPR; then
+  # do stuff
+elif EXPR; then
+  # do other stuff
+else
+  # final else
+fi
+</source>
+Note: sometimes you want to comment out a section of an if/else block, or maybe it does nothing at all.  In this case, you'll get an error.  To avoid the error, you can use the bash built-in <code>:</code> (colon command)
+<pre>
+ : [arguments]
+</pre>
+Do nothing beyond expanding arguments and performing redirections. The return status is zero.
+<source lang="bash">
+if [ -f "/tmp/Non-existing-file.txt" ] ; then
+  echo "I found the non-existing file"
+else
+  : # the colon command prevents an error if there are no other statements in this block
+fi
 </source>