recherche script de mécanisme de redirection

bonjour,

je suis à la recherche d'un exemple de script unix (un programme appelé dansbin, par ex)qui prendrait un nom de commande en argument et qui afficherait 0 si cette commande est présente dans /bin et une valeur différente de 0 sinon:

$ dansbin ls

0

$dansbin who

2

$

Merci pour vos futures réponses

man bash si c'est un script bash, man sh si c'est du bourne shell, etc...

Regarde la section "CONDITIONAL EXPRESSIONS"

CONDITIONAL EXPRESSIONS

Conditional expressions are used by the [[ compound command and the test and [ builtin commands to test file attributes and perform string and arithmetic comparisons. Expressions are formed from the

following unary or binary primaries. If any file argument to one of the primaries is of the form /dev/fd/n, then file descriptor n is checked. If the file argument to one of the primaries is one of

/dev/stdin, /dev/stdout, or /dev/stderr, file descriptor 0, 1, or 2, respectively, is checked.

Unless otherwise specified, primaries that operate on files follow symbolic links and operate on the target of the link, rather than the link itself.

See the description of the test builtin command (section SHELL BUILTIN COMMANDS below) for the handling of parameters (i.e. missing parameters).

-a file

True if file exists.

-b file

True if file exists and is a block special file.

-c file

True if file exists and is a character special file.

-d file

True if file exists and is a directory.

-e file

True if file exists.

-f file

True if file exists and is a regular file.

-g file

True if file exists and is set-group-id.

-h file

True if file exists and is a symbolic link.

-k file

True if file exists and its ‘‘sticky’’ bit is set.

-p file

True if file exists and is a named pipe (FIFO).

-r file

True if file exists and is readable.

-s file

True if file exists and has a size greater than zero.

-t fd True if file descriptor fd is open and refers to a terminal.

-u file

True if file exists and its set-user-id bit is set.

-w file

True if file exists and is writable.

-x file

True if file exists and is executable.

-O file

True if file exists and is owned by the effective user id.

-G file

True if file exists and is owned by the effective group id.

-L file

True if file exists and is a symbolic link.

-S file

True if file exists and is a socket.

-N file

True if file exists and has been modified since it was last read.

file1 -nt file2

True if file1 is newer (according to modification date) than file2, or if file1 exists and file2 does not.

file1 -ot file2

True if file1 is older than file2, or if file2 exists and file1 does not.

file1 -ef file2

True if file1 and file2 refer to the same device and inode numbers.

-o optname

True if shell option optname is enabled. See the list of options under the description of the -o option to the set builtin below.

-z string

True if the length of string is zero.

string

-n string

True if the length of string is non-zero.

string1 == string2

True if the strings are equal. = may be used in place of == for strict POSIX compliance.

string1 != string2

True if the strings are not equal.

string1 < string2

True if string1 sorts before string2 lexicographically in the current locale.

string1 > string2

True if string1 sorts after string2 lexicographically in the current locale.

arg1 OP arg2

OP is one of -eq, -ne, -lt, -le, -gt, or -ge. These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than

or equal to arg2, respectively. Arg1 and arg2 may be positive or negative integers.

ce qui donne

if [ -x /bin/$1 ]; then echo 1; else echo 0; fi

Ou

[ ! -x /bin/$1 ]; echo $?

Y'a moyen de faire avec which aussi, si on veut chercher dans tout le PATH :

 $ if which $CMD 1>/dev/null 2>/dev/null
then
exit 0
else
exit 1
fi

Je vais encore faire mon chipoteur

1>/dev/null 2>/dev/null

peut se remplacer au choix par

&>/dev/null

ou

&>-

Aussi encore une fois pas besoin de if, mais juste de la valeur de retour de which.

/usr/bin/which bli &>-; echo $?

C'était plus fait pour être pédagogique que concis

Je sais bien, mais ces version peuvent toujours intéresser des personnes