cocoa - NSTask:进程的启动路径是否存在

Question

此代码用于获取进程的标准输出

    NSTask       * task;
    NSPipe       * pipe;
    NSFileHandle * fileHandle;

    task       = [ [ NSTask alloc ] init ];
    pipe       = [ NSPipe pipe ];
    fileHandle = [ pipe fileHandleForReading ];

    [ task setLaunchPath: @"/usr/bin/lspci" ];
    [ task setArguments:[NSArray arrayWithObject:@"-nn"]];
    [ task setStandardOutput: pipe ];
    [ task setStandardError: pipe ];
    [ task launch ];
    [ task waitUntilExit]; 
    [ task release];

    NSData *outputData = [[pipe fileHandleForReading] readDataToEndOfFile];

    NSString *outputString = [[[NSString alloc] initWithData:outputData encoding:NSUTF8StringEncoding] autorelease];

由于某些系统上不存在/usr/bin/lspci，因此出现此 fatal error

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'launch path not accessible'

如何事先检查lspci是否存在，如果不存在则向用户显示错误消息？

Answer 1

检查文件是否存在且可执行:

BOOL exists = [[NSFileManager defaultManager] isExecutableFileAtPath:[task launchPath]];

丢失文件并不是您遇到异常的唯一原因。您应该始终使用 @try-@catch block 。