Sleep command in sh with variables
As others have indicated, the modern(*) approach is to use #!/bin/bash or even #!/bin/ksh with their built-in support of arithmetic operations using n=$(($a+$b+$c).
As you have explicitly mentioned #!/bin/sh, here is a solution that will work for you.
#!/bin/shecho hello1a=6b=2c=3d=`echo "$a+$b+$c" | bc`sleep $decho hello2The key part is using backquotes for command-substitution, and sending the math arguments to be evaluated by the bc command, using the shell's pipe (|) functionality: i.e.
d=`echo "$a+$b+$c" | bc` | | | | | -> bc is a "basic" calulator | | | | -> pipes pass std-out from preceding cmd, to std in fo following cmd | | | -> a string to be passed to `bc` for arthimetic evaluation | | -> echo writes its output to std-out | -> = assigns output of cmd=substition to var $d(*) modern in shells means 1986 and later ;-)
IHTH