objective c - executing shell command with | (pipe) using NSTask -

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i'm trying execute comamnd ps -ef | grep test using nstask can't | grep test included in nstask:

this i'm using output of ps -ef string need somehow pid of process test

nstask *task; task = [[nstask alloc] init]; [task setlaunchpath: @"/bin/ps"];  nsarray *arguments; arguments = [nsarray arraywithobjects: @"-ef", nil]; [task setarguments: arguments];     nspipe *pipe; pipe = [nspipe pipe]; [task setstandardoutput: pipe];  nsfilehandle *file; file = [pipe filehandleforreading];  [task launch];  nsdata *data; data = [file readdatatoendoffile];  nsstring *string; string = [[nsstring alloc] initwithdata: data                                encoding: nsutf8stringencoding]; nslog (@"got\n%@", string);

piping feature provided shells, such /bin/sh. may try launching command via such shell:

/* ... */ [task setlaunchpath: @"/bin/sh"]; /* ... */ arguments = [nsarray arraywithobjects: @"-c", @"ps -ef | grep test", nil];

however, if let user supply value (instead of hard-coding e.g. test), making program susceptible shell injection attacks, kind of sql injection. alternative, doesn't suffer problem, use pipe object connect standard output of ps standard input of grep:

nstask *pstask = [[nstask alloc] init]; nstask *greptask = [[nstask alloc] init];  [pstask setlaunchpath: @"/bin/ps"]; [greptask setlaunchpath: @"/bin/grep"];  [pstask setarguments: [nsarray arraywithobjects: @"-ef", nil]]; [greptask setarguments: [nsarray arraywithobjects: @"test", nil]];  /* ps ==> grep */ nspipe *pipebetween = [nspipe pipe]; [pstask setstandardoutput: pipebetween]; [greptask setstandardinput: pipebetween];  /* grep ==> me */ nspipe *pipetome = [nspipe pipe]; [greptask setstandardoutput: pipetome];  nsfilehandle *grepoutput = [pipetome filehandleforreading];  [pstask launch]; [greptask launch];  nsdata *data = [grepoutput readdatatoendoffile];  /* etc. */

this uses built-in foundation functionality perform same steps shell when encounters | character.

finally others have pointed out, usage of grep overkill. add code:

nsarray *lines = [string componentsseparatedbystring:@"\n"]; nsarray *filteredlines = [lines filteredarrayusingpredicate: [nspredicate predicatewithformat: @"self contains[c] 'test'"]];

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