iphone - How to capture standard output of the process started by system() -

iphone - How to capture standard output of the process started by system() -

how save output of system("openssl enc -aes-128-cbc -k secret -p -md sha1 > filename") file.

i have tried following:

nsarray *paths = nssearchpathfordirectoriesindomains (nsdocumentdirectory, nsuserdomainmask, yes); nsstring *documentsdirectory = [paths objectatindex:0]; nsstring *filename = [nsstring stringwithformat:@"%@/textfile.txt", documentsdirectory]; nsstring *str=[nsstring stringwithformat:@"openssl enc -aes-128-cbc -k secret -p -md sha1 > %s",[filename utf8string]]; nslog(@"aes key %@",str); system([str utf8string]); nsstring *straes = [nsstring stringwithcontentsoffile:filename encoding:nil error:nil]; nslog(@"straes key %@",straes); nsstring *straeskey=[[[[straes componentsseparatedbystring:@"\n"] objectatindex:1] componentsseparatedbystring:@"="] objectatindex:1]; nslog(@"straeskey key %@",straeskey); // nsstring *content = @"one\ntwo\nthree\nfour\nfive"; [str writetofile:filename atomically:no encoding:nsstringencodingconversionallowlossy error:nil];`

where going wrong ?

the system() function sends output console since iphone not have console, need redirect output text file , key file utilize encryption/decryption.

first of all: aware, don't think can utilize system(3) on not jail broken ios. i'm not sure, explain how it:

this little bit tricky.

to accomplish it, have know each process gets opened 3 file descriptors: 1 reading (stdin standard input) , 2 writing (stdout standard output , stderr standard error output). have fd numbers 0 (stdin), 1 (stdout) , 2 (stderr).

to redirect standard output or standard error file program, have following:

first, fork(2) process. in parent process waitpid(2) kid prozess. in kid process: reopen (freopen(3)) stdout , stderr file want output redirected. use execve(2) execute programme want call when command terminates, parent gets sigchld , waitpid(2) should return

the number in brackets describes chapter in man pages (man 2 waitpid, e.g.) function.

hope helps, if have more questions, inquire :-)

update: since op wants output , not specificly file, can utilize popen(3):

int status; char value[1024]; file *fp = popen("openssl enc -aes-128-cbc -k secret -p -md sha1", "r"); if (fp == null) exit(1); // handle error while (fgets(value, 1024, fp) != null) { printf("value: %s", value); } status = pclose(fp); if (status == -1) { /* error reported pclose() */ } else { /* utilize macros described under wait() inspect `status' in order determine success/failure of command executed popen() */ }

iphone ios io-redirection