{"id":1855,"date":"2022-09-06T21:16:07","date_gmt":"2022-09-06T19:16:07","guid":{"rendered":"http:\/\/www.fabienm.eu\/wordpress\/?p=1855"},"modified":"2022-09-06T21:16:08","modified_gmt":"2022-09-06T19:16:08","slug":"retour-de-string-en-rust","status":"publish","type":"post","link":"https:\/\/www.fabienm.eu\/wordpress\/2022\/09\/06\/retour-de-string-en-rust\/","title":{"rendered":"Retour de String en Rust"},"content":{"rendered":"\n

Alors voila, je veux \u00e9crire une fonction qui appelle une commande shell et retourne la cha\u00eene de caract\u00e8res.<\/p>\n\n\n\n

Avec la cagette standard std::process::Command<\/a> c’est plut\u00f4t simple il suffit de faire \u00e7a :<\/p>\n\n\n

use<\/span> std<\/span>::process<\/span>::Command<\/span>;\n\/\/..<\/span>\n    let _cmdret = Command::new(\"cd-discid\"<\/span>)\n                            .output()\n                            .expect(\"La commande cd-discid a \u00e9chou\u00e9e\"<\/span>);\n  \n\/\/..<\/span><\/code><\/span>Langage du code\u00a0:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
println!(\"{:?}\"<\/span>, &_cmdret);\n\/\/:Sortie -><\/span>\nOutput { status<\/span>: ExitStatus(unix_wait_status(0<\/span>)), stdout<\/span>: \"30027f05 5 150 2422 15072 29219 44022 641\\n\"<\/span>, stderr<\/span>: \"\"<\/span> }\n<\/code><\/span>Langage du code\u00a0:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Pour le moment c’est assez simple, si je veux r\u00e9cup\u00e9rer la cha\u00eene de caract\u00e8res, il me suffit de prendre le champs stdout<\/code> :<\/p>\n\n\n
println!(\"{:?}\"<\/span>, &_cmdret.stdout);\n\/\/...<\/span>\n[51<\/span>, 48<\/span>, 48<\/span>, 50<\/span>, 55<\/span>, 102<\/span>, 48<\/span>, 53<\/span>, 32<\/span>, 53<\/span>, 32<\/span>, 49<\/span>, 53<\/span>, 48<\/span>, 32<\/span>, 50<\/span>, 52<\/span>, 50<\/span>, 50<\/span>, 32<\/span>, 49<\/span>, 53<\/span>, 48<\/span>, 55<\/span>, 50<\/span>, 32<\/span>, 50<\/span>, 57<\/span>, 50<\/span>, 49<\/span>, 57<\/span>, 32<\/span>, 52<\/span>, 52<\/span>, 48<\/span>, 50<\/span>, 50<\/span>, 32<\/span>, 54<\/span>, 52<\/span>, 49<\/span>, 10<\/span>]<\/code><\/span>Langage du code\u00a0:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Allons bon, convertissons avec std::str<\/a> :<\/p>\n\n\n
use std::str\n\/\/\/<\/span>\n    println!(\"{:?}\"<\/span>, str<\/span>::from_utf8(&_cmdret.stdout));\n\/\/\/sortie -><\/span>\nOk(\"30027f05 5 150 2422 15072 29219 44022 641\\n\"<\/span>)\n<\/code><\/span>Langage du code\u00a0:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
\/\/\/ Lit le num\u00e9ro unique du CD se trouvant dans le lecteur<\/span>\npub fn get_discid() -> Result<String<\/span>, Box<dyn Error<\/span>>> {\n    let<\/span> _cmdret = Command::new<\/span>(\"cd-discid\"<\/span>)\n                            .output()\n                            .expect(\"La commande cd-discid a \u00e9chou\u00e9e\"<\/span>);\n\n    str::from_utf8(&_cmdret.stdout)\n}<\/code><\/span>Langage du code\u00a0:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
22<\/span> |     str::from_utf8(&_cmdret.stdout)\n   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `std::string::String`, found `&str`\n<\/code><\/span>Langage du code\u00a0:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
22<\/span> |     Ok(str::from_utf8(&_cmdret.stdout))\n   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `std::string::String`, found enum `Result`\n<\/code><\/span>Langage du code\u00a0:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Et c’est l\u00e0 que je commence \u00e0 perdre pied, bin oui t’as trouv\u00e9 un enum Result, puisque c’est \u00e7a que j’attends en retour patate !<\/p>\n\n\n\n
\/\/\/ Lit le num\u00e9ro unique du CD se trouvant dans le lecteur<\/span>\npub fn get_discid() -> Result<String<\/span>, Box<dyn Error<\/span>>> {\n    let<\/span> _cmdret = Command::new<\/span>(\"cd-discid\"<\/span>)\n                            .output()\n                            .expect(\"La commande cd-discid a \u00e9chou\u00e9e\"<\/span>);\n\n    match str::from_utf8(&_cmdret.stdout) {\n        Ok(v) => Ok(v.to_string()),\n        Err(e) => Err(e.into())\n    }\n}<\/code><\/span>Langage du code\u00a0:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Bon maintenant \u00e7a marche. Mais il me reste un go\u00fbt amer de celui qui n’a pas compris ce qu’il a \u00e9crit. Et j’ai la d\u00e9sagr\u00e9able impression d’avoir tartin\u00e9 du code pour pas grand chose !<\/p>\n\n\n\n
On doit pouvoir faire plus simple non ?<\/p>\n\n\n\n
Bref, la route est encore longue, et c’est pas ce soir que je verrais mes recettes d’histoires<\/a> termin\u00e9es \ud83d\ude09<\/p>\n","protected":false},"excerpt":{"rendered":"
Alors voila, je veux \u00e9crire une fonction qui appelle une commande shell et retourne la cha\u00eene de caract\u00e8res. Avec la cagette standard std::process::Command c’est plut\u00f4t simple il suffit de faire \u00e7a : L’affichage de _cmdret avec un println! qui va … Continuer la lecture →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[263,143,191,276],"class_list":["post-1855","post","type-post","status-publish","format-standard","hentry","category-non-classe","tag-humeur","tag-programmation","tag-rust","tag-string"],"_links":{"self":[{"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1855","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/comments?post=1855"}],"version-history":[{"count":4,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1855\/revisions"}],"predecessor-version":[{"id":1859,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/posts\/1855\/revisions\/1859"}],"wp:attachment":[{"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/media?parent=1855"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/categories?post=1855"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fabienm.eu\/wordpress\/wp-json\/wp\/v2\/tags?post=1855"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\u00c0 noter qu’il est possible de remplacer le to_string()<\/a> en into()<\/a> dans le Ok()<\/code> mais pas pour le Err()<\/code>.<\/p>\n\n\n\n
En browsant d\u00e9sesp\u00e9r\u00e9ment le web j’ai cru trouver qu’il fallait faire un match<\/a> sur l’enum pour retourner un nouvel enum (mais j’ai pas compris pourquoi le premier ne convenait pas):<\/p>\n\n\n
Rajoutons un Ok()<\/a> pour lui faire plaisir alors :<\/p>\n\n\n
Sauf que non, ce que je croyais \u00eatre un enum<\/a> \u00abResult\u00bb c’est transform\u00e9 en une cha\u00eene de caract\u00e8res &str<\/a> :<\/p>\n\n\n
On obtient donc une sortie de type Result<\/a> non ? Notre fonction doit pouvoir s’\u00e9crire comme \u00e7a alors :<\/p>\n\n\n
Rhaa, mais pourquoi \u00e7a s’est transform\u00e9 en vecteur de u8<\/a> ?!<\/p>\n\n\n\n
L’affichage de _cmdret avec un println!<\/a> qui va bien me donne la forme de la structure retourn\u00e9e :<\/p>\n\n\n