launch bash without using any letters

$0
Starts a new shell (in bash/sh, it starts bash/sh). 'man bash' explains: "If arguments remain after option processing, and neither the -c nor the -s option has been supplied, the first argument is assumed to be the name of a file containing shell commands. If bash is invoked in this fashion, $0 is set to the name of the file, and the positional parameters are set to the remaining arguments."

0
By: fhtagn
2013-03-05 22:57:14

2 Alternatives + Submit Alt

  • ry4an@four:~$ echo $SHLVL 1 ry4an@four:~$ ${0/-/} ry4an@four:~$ echo $SHLVL 2


    7
    ${0/-/}
    ry4an · 2012-12-31 17:43:08 0
  • I don't know why anyone would use this, I was just messing around tonight and managed to start bash without using any letters and thought I would share. It's pretty simple, first it tries to execute "-" redirecting stderr to stdout which prints the error "bash: -: command not found" to standard output, then I try to execute "bash: -: command not found" which produces the output "bash: bash: -: command not found: command not found". lastly, (on the other side of the semicolon) I use the underscore environment variable which refers to the last command run ("bash: -: command not found") and take out everything after the first ":" character using brace expressions and your left with "bash" Show Sample Output


    6
    "$(- 2>&1)";${_%%:*}
    LinuxMan · 2012-12-29 09:21:09 2

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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