Dotaz: BASH - expanze na prikazovem radku

[Michal]

jsem zacatecnik s unixem a trosicku jsem se zamotal, potrebuji ve scriptu pomoci obsahu jedne promenne sestavit nazev jine promenne a zobrazit jeji obsah....uvedu mensi priklad

TEXT_FERDA="ja jsem Ferda"
TEXT_KAREL="ja jsem Karel"

JMENO=FERDA
echo "Ahoj $"TEXT_`echo $JMENO`""

to co je v kodu tucnou kurzivou mi nefunguje...poradi nekdo, urcite to bude jednoduche jen ja si s tim nevim rady

Odpovědi

[Semo]

RTFM bash:

... Parameter Expansion ... If the first character of parameter is an exclamation point, a level of variable indirection is introduced. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is known as indirect expansion. The exceptions to this are the expansions of ${!prefix*} and ${!name[@]} described below. The exclamation point must immediately follow the left brace in order to introduce indirection.

[Michal Kubeček]

Tj. např.

  v="TEXT_$JMENO"
  echo "... ${!v}"