dash-shell

This question already has an answer here: Why do shell script comparisons often use x$VAR = xyes? 7 answers What is the portable and canonical way to test if variable is empty/undefined in a shell script? It should work in all sh-like shells. What I do now is something like: if [ -z "$var" ] ; then ... and for reverse, doing something when variable is not empty/undefined: if [ -n "$var" ] ; then ... And while these work for the scripts I write now, I'd like to know a way, that will work in any reasonably compatible sh -like shell , even on some more obscure environment than a Linux PC with GNU

I have a problem implementing a for loop. I get this error when I execute my script test1.sh: 2: Syntax error: Bad for loop variable I don't understand this error. This is my script #!/bin/bash for (( c=1; c<=5; c++ )) do echo "Welcome $c times..." done can any one tell me syntax for for loop in sh(in ubuntu it links to dash shell) shell in ubuntu? You probably run it with sh , not bash . Try bash test1.sh , or ./test1.sh if it's executable, but not sh test1.sh . A standard POSIX shell only accepts the syntax for varname in list The C-like for-loop syntax for (( expr1; expr2; expr3 )) is a

How and who determines what executes when a Bash-like script is executed as a binary without a shebang? I guess that running a normal script with shebang is handled with binfmt_script Linux module, which checks a shebang, parses command line and runs designated script interpreter. But what happens when someone runs a script without a shebang? I've tested the direct execv approach and found out that there's no kernel magic in there - i.e. a file like that: $ cat target-script echo Hello echo "bash: $BASH_VERSION" echo "zsh: $ZSH_VERSION" Running compiled C program that does just an execv call