{"id":33494,"date":"2019-10-31T21:52:52","date_gmt":"2019-10-31T18:52:52","guid":{"rendered":"https:\/\/prohoster.info\/blog\/sem-neozhidannyh-peremennyh-bash\/"},"modified":"2019-10-31T21:52:52","modified_gmt":"2019-10-31T18:52:52","slug":"sem-neozhidannyh-peremennyh-bash","status":"publish","type":"post","link":"https:\/\/prohoster.info\/ro\/blog\/administrirovanie\/sem-neozhidannyh-peremennyh-bash","title":{"rendered":"\u0218apte variabile nea\u0219teptate Bash","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Continu\u00e2nd seria de note despre func\u021bii mai pu\u021bin cunoscute<\/a><\/noindex> bash, v\u0103 voi ar\u0103ta \u0219apte variabile despre care s-ar putea s\u0103 nu \u0219ti\u021bi.<\/a><\/noindex> PROMPT_COMMAND<\/p>\n

1) Probabil c\u0103 deja \u0219ti\u021bi cum s\u0103 manipula\u021bi promptul pentru a ar\u0103ta diferite informa\u021bii utile, dar nu toat\u0103 lumea \u0219tie c\u0103 de fiecare dat\u0103 c\u00e2nd se afi\u0219eaz\u0103 promptul, poate fi rulat\u0103 o comand\u0103 de shell.<\/code><\/h4>\n

\nDe fapt, mul\u021bi manipulatori complec\u0219i ai promptului folosesc aceast\u0103 variabil\u0103 pentru a executa comenzi care colecteaz\u0103 informa\u021bii ce vor fi afi\u0219ate \u00een prompt.<\/p>\n

\u00cencerca\u021bi s\u0103 rula\u021bi asta \u00eentr-un shell nou \u0219i ve\u021bi vedea ce se \u00eent\u00e2mpl\u0103 cu sesiunea:<\/p>\n

$ PROMPT_COMMAND='echo -n \"writing the prompt at \" && date'<\/p>\n

HISTTIMEFORMAT<\/code><\/pre>\n
<\/a><\/noindex><\/p>\n
2) \u00een consol\u0103, ve\u021bi ob\u021bine o list\u0103 cu comenzile efectuate anterior sub contul dvs.<\/code><\/h4>\n
\nDac\u0103 se ruleaz\u0103 history<\/code> $ HISTTIMEFORMAT='I ran this at: %d\/%m\/%y %T '<\/p>\n
Odat\u0103 ce aceast\u0103 variabil\u0103 a fost setat\u0103, noile \u00eenregistr\u0103ri vor salva timpul \u00eempreun\u0103 cu comanda, deci ie\u0219irea va ar\u0103ta astfel:<\/code><\/pre>\n
\n1871  I ran this at: 01\/05\/19 13:38:07 cat \/etc\/resolv.conf\n1872  I ran this at: 01\/05\/19 13:38:19 curl bbc.co.uk\n1873  I ran this at: 01\/05\/19 13:38:41 sudo vi \/etc\/resolv.conf\n1874  I ran this at: 01\/05\/19 13:39:18 curl -vvv bbc.co.uk\n1876  I ran this at: 01\/05\/19 13:39:25 sudo su -<\/p>\n
Formatoarea corespunde caracterelor din<\/pre>\n
\nman date CDPATH<\/code>.<\/p>\n
3) Pentru a economisi timp \u00een linia de comand\u0103, pute\u021bi folosi aceast\u0103 variabil\u0103 pentru a schimba folderele la fel de u\u0219or cum apela\u021bi comenzile.<\/code><\/h4>\n
\n, variabila<\/p>\n
Cum \u0219i PATH<\/code>reprezint\u0103 o list\u0103 de c\u0103i separate prin dou\u0103 puncte. C\u00e2nd rula\u021bi o comand\u0103 Pentru a economisi timp \u00een linia de comand\u0103, pute\u021bi folosi aceast\u0103 variabil\u0103 pentru a schimba folderele la fel de u\u0219or cum apela\u021bi comenzile.<\/code> cu o cale relativ\u0103 (adic\u0103 f\u0103r\u0103 slash la \u00eenceput), implicit shell-ul caut\u0103 \u00een folderul local pentru numele corespunz\u0103toare. cd<\/code> va c\u0103uta \u00een c\u0103ile pe care le-a\u021bi dat pentru directorul \u00een care dori\u021bi s\u0103 merge\u021bi. Pentru a economisi timp \u00een linia de comand\u0103, pute\u021bi folosi aceast\u0103 variabil\u0103 pentru a schimba folderele la fel de u\u0219or cum apela\u021bi comenzile.<\/code> Dac\u0103 seta\u021bi<\/p>\n
\u00een acest mod: Pentru a economisi timp \u00een linia de comand\u0103, pute\u021bi folosi aceast\u0103 variabil\u0103 pentru a schimba folderele la fel de u\u0219or cum apela\u021bi comenzile.<\/code> $ CDPATH=\/:\/lib<\/p>\n
\u0219i apoi introduce\u021bi:<\/code><\/pre>\n
\n$ cd \/home\n$ cd tmp<\/p>\n
atunci ve\u021bi ajunge \u00eentotdeauna \u00een<\/code><\/pre>\n
\nindiferent de locul \u00een care v\u0103 afla\u021bi. \/tmp<\/code> Totu\u0219i, ave\u021bi grij\u0103, c\u0103ci dac\u0103 nu include\u021bi folderul local (<\/p>\n
) \u00een list\u0103, nu ve\u021bi putea crea niciun alt folder.<\/code>tmp \u0219i s\u0103 merge\u021bi la el, ca de obicei:<\/code> $ cd \/home\n$ mkdir tmp\n$ cd tmp\n$ pwd\n\/tmp<\/p>\n
Ups!<\/code><\/pre>\n
\nAceasta pare a fi o confuzie pe care am sim\u021bit-o c\u00e2nd am realizat c\u0103 folderul local nu a fost inclus \u00een variabila mai familiar\u0103<\/p>\n
\u2026 dar trebuie s\u0103 face\u021bi asta \u00een variabila PATH, pentru c\u0103 a\u021bi putea fi p\u0103c\u0103lit, rul\u00e2nd o comand\u0103 fals\u0103 dintr-un cod desc\u0103rcat. PATH<\/code>Punctul meu de plecare este:<\/p>\n
CDPATH=.:\/space:\/etc:\/var\/lib:\/usr\/share:\/opt<\/p>\n
SHLVL<\/code><\/pre>\n
<\/p>\n
4) V-a\u021bi \u00eentrebat vreodat\u0103, introduc\u00e2nd<\/code><\/h4>\n
\nV-a\u021bi g\u00e2ndit vreodat\u0103, introduc\u00e2nd exit<\/code> v\u0103 va scoate din shell-ul bash curent \u00eentr-un alt shell \u201ep\u0103rinte\u201d sau pur \u0219i simplu va \u00eenchide complet fereastra consolei?<\/p>\n
Aceast\u0103 variabil\u0103 urm\u0103re\u0219te c\u00e2t de ad\u00e2nc a\u021bi fost \u00een shell-ul bash. Dac\u0103 crea\u021bi un nou terminal, aceasta este setat\u0103 pe 1:<\/p>\n
$ echo $SHLVL\n1<\/code><\/pre>\n
\nApoi, dac\u0103 lansa\u021bi un alt proces al shell-ului, num\u0103rul cre\u0219te:<\/p>\n
$ bash\n$ echo $SHLVL\n2<\/code><\/pre>\n
\nAcest lucru poate fi foarte util \u00een scripturi, unde nu sunte\u021bi sigur dac\u0103 trebuie s\u0103 ie\u0219i\u021bi sau nu, sau pentru a urm\u0103ri unde v\u0103 afla\u021bi \u00een ierarhie.<\/p>\n
5) LINENO<\/code><\/h4>\n
\nDe asemenea, pentru analiza st\u0103rii curente \u0219i depanare, variabila LINENO<\/code>, care raporteaz\u0103 num\u0103rul de comenzi executate \u00een sesiune p\u00e2n\u0103 \u00een prezent:<\/p>\n
$ bash\n$ echo $LINENO\n1\n$ echo $LINENO\n2<\/code><\/pre>\n
\nAcest lucru este folosit cel mai frecvent la depanarea scripturilor. Inser\u00e2nd astfel de linii precum echo DEBUG:$LINENO<\/code>, pute\u021bi determina rapid unde v\u0103 afla\u021bi \u00een script (sau nu).<\/p>\n
6) REPLY<\/code><\/h4>\n
\nDac\u0103, ca mine, tinde\u021bi s\u0103 scrie\u021bi un astfel de cod:<\/p>\n
$ read input\necho face\u021bi ceva cu $input<\/code><\/pre>\n
\natunci poate fi surprinz\u0103tor c\u0103 nu trebuie s\u0103 v\u0103 face\u021bi griji deloc \u00een leg\u0103tur\u0103 cu crearea unei variabile:<\/p>\n
$ read\necho face\u021bi ceva cu $REPLY<\/code><\/pre>\n
\nAcest lucru face acela\u0219i lucru.<\/p>\n
7) TMOUT<\/code><\/h4>\n
\nPentru a nu r\u0103m\u00e2ne pe serverele de produc\u021bie prea mult timp din motive de siguran\u021b\u0103 sau pentru a nu rula accidental ceva periculos \u00een terminalul gre\u0219it, setarea acestei variabile ac\u021bioneaz\u0103 ca o protec\u021bie.<\/p>\n
Dac\u0103 nu se introduce nimic timp de un anumit num\u0103r de secunde, se va ie\u0219i din shell.<\/p>\n
Adic\u0103, aceasta este o alternativ\u0103 la sleep 1 && exit<\/code>:<\/p>\n
$ TMOUT=1<\/code><\/pre>\n
Sursa: habr.com<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"
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