Accessing bash command line args vs

Question

In many SO questions and bash tutorials I see that I can access command line args in bash scripts in two ways        gt cat testargs sh     bin bash  echo  you passed me     echo  you passed me       Which results in       gt  bash testargs sh arg1 arg2 you passed me arg1 arg2 you passed me arg1 arg2   What is the difference between    and     When should one use the former and when shall one use the latter

User · Accepted Answer

The difference appears when the special parameters are quoted. Let me illustrate the differences:

$ set -- "arg  1" "arg  2" "arg  3"

$ for word in $*; do echo "$word"; done
arg
1
arg
2
arg
3

$ for word in $@; do echo "$word"; done
arg
1
arg
2
arg
3

$ for word in "$*"; do echo "$word"; done
arg  1 arg  2 arg  3

$ for word in "$@"; do echo "$word"; done
arg  1
arg  2
arg  3

one further example on the importance of quoting: note there are 2 spaces between "arg" and the number, but if I fail to quote $word:

$ for word in "$@"; do echo $word; done
arg 1
arg 2
arg 3

and in bash, "$@" is the "default" list to iterate over:

$ for word; do echo "$word"; done
arg  1
arg  2
arg  3

User · Answer

A nice handy overview table from the Bash Hackers Wiki      Syntax Effective result         1  2  3       N        1  2  3       N     quot    quot   quot  1c 2c 3c   c  N  quot     quot    quot   quot  1 quot   quot  2 quot   quot  3 quot       quot   N  quot      where c in the third row is the first character of  IFS  the Input Field Separator  a shell variable  If the arguments are to be stored in a script variable and the arguments are expected to contain spaces  I wholeheartedly recommend employing a  quot    quot  trick with the input field separator set to tab IFS    t

User · Answer

Expands to the positional parameters  starting from one  When the   expansion occurs within double quotes  it expands to a single word   with the value of each parameter separated by the first character of   the IFS special variable  That is       is equivalent to   1c 2c        where c is the first character of the value of the IFS variable  If   IFS is unset  the parameters are separated by spaces  If IFS is null    the parameters are joined without intervening separators           Expands to the positional parameters  starting from one  When the   expansion occurs within double quotes  each parameter expands to a   separate word  That is       is equivalent to   1    2      If the   double-quoted expansion occurs within a word  the expansion of the   first parameter is joined with the beginning part of the original   word  and the expansion of the last parameter is joined with the last   part of the original word  When there are no positional parameters         and    expand to nothing  i e   they are removed     Source  Bash man

User · Answer

This example let may highlight the differ between  at  and  asterix  while we using them  I declared two arrays  fruits  and  vegetables   fruits  apple pear plumm peach melon              vegetables  carrot tomato cucumber potatoe onion   printf  Fruits  t s n     fruits                  printf  Fruits  t s n     fruits                  echo   ---------------------------------------------         printf  Vegetables  t s n     vegetables          printf  Vegetables  t s n     vegetables            See the following result the code above   Fruits  apple pear plumm peach melon Fruits  apple Fruits  pear Fruits  plumm Fruits  peach Fruits  melon   ---------------------------------------------   Vegetables  carrot tomato cucumber potatoe onion Vegetables  carrot Vegetables  tomato Vegetables  cucumber Vegetables  potatoe Vegetables  onion

User · Answer

is same as     but each parameter is a quoted string  that is  the parameters are passed on intact  without interpretation or expansion  This means  among other things  that each parameter in the argument list is seen as a separate word   Of course       should be quoted   http   tldp org LDP abs html internalvariables html ARGLIST

[bash] Accessing bash command line args $@ vs $*

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