How can I add a help method to a shell script

Question

How do I check if a -h attribute has been passed into a shell script   I would like to display a help message when a user calls myscript sh -h

User · Answer

For a quick single option solution  use if  If you only have a single option to check and it will always be the first option   1  then the simplest solution is an if with a test      For example   if     1      -h      then     echo  Usage   basename  0   -h       exit 0 fi   Note that for posix compatibility   will work as well as      Why quote  1   The reason the  1 needs to be enclosed in quotes is that if there is no  1 then the shell will try to run if        -h    and fail because    has only been given a single argument when it was expecting two           -h    bash         unary operator expected   For anything more complex use getopt or getopts  As suggested by others  if you have more than a single simple option  or need your option to accept an argument  then you should definitely go for the extra complexity of using getopts   As a quick reference  I like The 60 second getopts tutorial  dagger   You may also want to consider the getopt program instead of the built in shell getopts  It allows the use of long options  and options after non option arguments  e g  foo a b c --verbose rather than just foo -v a b c   This Stackoverflow answer explains how to use GNU getopt    dagger  jeffbyrnes mentioned that the original link died but thankfully the way back machine had archived it

User · Answer

here is a part I use it to start a VNC server      bin bash start     echo  Starting vnc server with  resolution on Display  display   your execute command here mine is below  vncserver   display -geometry  resolution    stop     echo  Killing vncserver on display  display   vncserver -kill   display                                The command line help                             display help         echo  Usage   0  option      start stop restart    gt  amp 2     echo     echo     -r  --resolution           run with the given resolution WxH      echo     -d  --display              Set on which display to host on       echo       echo some stuff here for the -a or --add-options      exit 1                                       Check if parameters options      are given on the commandline                                    while   do     case   1  in       -r   --resolution            if      -ne 0    then             resolution   2      You may want to check validity of  2           fi           shift 2                    -h   --help            display help    Call your function           exit 0                    -d   --display            display   2             shift 2                      -a   --add-options              do something here call function             and write it in your help function display help              shift 2                      --    End of all options           shift           break                    -             echo  Error  Unknown option   1   gt  amp 2              or call function display help           exit 1                           No more options           break                  esac done                            Check if parameter     is set too execute                          case   1  in   start      start   calling function start            stop      stop   calling function stop            restart      stop    calling function stop       start   calling function start                    echo  Usage   0  start stop restart    gt  amp 2      display help       exit 1         esac   It s a bit weird that I placed the start stop restart in a separate case but it should work

User · Answer

here s an example for bash  usage  quot   basename  quot  0 quot    -h   -s n  -- program to calculate the answer to life  the universe and everything  where      -h  show this help text     -s  set the seed value  default  42  quot   seed 42 while getopts   hs   option  do   case  quot  option quot  in     h  echo  quot  usage quot         exit               s  seed  OPTARG                  printf  quot missing argument for - s n quot   quot  OPTARG quot   gt  amp 2        echo  quot  usage quot   gt  amp 2        exit 1                  printf  quot illegal option  - s n quot   quot  OPTARG quot   gt  amp 2        echo  quot  usage quot   gt  amp 2        exit 1             esac done shift    OPTIND - 1    To use this inside a function   use  quot  FUNCNAME quot  instead of   basename  quot  0 quot   add local OPTIND OPTARG before calling getopts

User · Answer

i think you can use case for this     case  1 in   -h  echo  usage       h  echo  usage    help  echo  usage    esac

User · Answer

Better to use getopt facility of bash  Please look at this Q amp A for more help  Using getopts in bash shell script to get long and short command line options

User · Answer

The first argument to a shell script is available as the variable  1  so the simplest implementation would be   if     1      -h     then   echo  Usage   basename  0   somestuff     exit 0 fi   But what anubhava said

[unix] How can I add a help method to a shell script?

For a quick single option solution, use `if`

Why quote `$1`?

For anything more complex use `getopt` or `getopts`

Examples related to unix

Examples related to shell

[unix] How can I add a help method to a shell script?

For a quick single option solution, use if

Why quote $1?

For anything more complex use getopt or getopts

Examples related to unix

Examples related to shell

For a quick single option solution, use `if`

Why quote `$1`?

For anything more complex use `getopt` or `getopts`