Question

假设我有这样一个文件：

    $ head -n 15 foo.md
    # User Database
    # 
    # Note that this file is consulted directly only when the system is running
    # in single-user mode.  At other times this information is provided by
    # Open Directory.
    #
    # See the opendirectoryd(8) man page for additional information about
    # Open Directory.
    ##
    nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false
    root:*:0:0:System Administrator:/var/root:/bin/sh
    daemon:*:1:1:System Services:/var/root:/usr/bin/false
    _uucp:*:4:4:Unix to Unix Copy Protocol:/var/spool/uucp:/usr/sbin/uucico
    _taskgated:*:13:13:Task Gate Daemon:/var/empty:/usr/bin/false

我想查看除'＃'之外的内容，
它可以通过反转选项来实现，比如

$ grep -v“^＃”＆lt; foo.md 我打算否定^

    $ grep -E "[^#]" < foo.md
    # User Database
    # 
    # Note that this file is consulted directly only when the system is running
    # in single-user mode.  At other times this information is provided by

并且

    $ grep -Eo "[^#]+" < foo.md
     User Database

     Note that this file is consulted directly only when the system is running
     in single-user mode.  At other times this information is provided by
     Open Directory.
     See the opendirectoryd(8) man page for additional information about
     Open Directory.
    nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false

命令未按我的意愿输出。

如何用否定来解决这个问题？

Answer 1

如果我是对的，你希望只有非评论行，最后5行，而不是以'＃'开头？

对于我来说，在Mac OS X或CentOS上使用grep -v“^＃”非常有效，输出中只有最后5行。

选项-v表示反转匹配，字符'^'表示'行的开头'

Answer 2

您的文件在- (NSManagedObjectContext *) managedObjectContext { NSThread *thisThread = [NSThread currentThread]; if (thisThread == [NSThread mainThread]) { //For the Main thread just return default context iVar if (managedObjectContext != nil) { return managedObjectContext; } NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator]; if (coordinator != nil) { managedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [managedObjectContext setPersistentStoreCoordinator: coordinator]; } return managedObjectContext; } else { //Return separate MOC for each new thread NSManagedObjectContext * threadManagedObjectContext = [[thisThread threadDictionary] objectForKey:@"MOC_KEY"]; if (threadManagedObjectContext == nil) { threadManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [threadManagedObjectContext setPersistentStoreCoordinator: [self persistentStoreCoordinator]]; [[thisThread threadDictionary] setObject:threadManagedObjectContext forKey:@"MOC_KEY"]; } return threadManagedObjectContext; } }之前有空格，因此您需要对其进行说明。这里不需要否定并使一切变得复杂 - 特别是在尝试反向匹配时，所以不要为此烦恼。

<强>输出：

grep -v "^\s*#" file.txt

要反过来，只需丢失反转匹配（nobody:*:-2:-2:Unprivileged User:/var/empty:/usr/bin/false root:*:0:0:System Administrator:/var/root:/bin/sh daemon:*:1:1:System Services:/var/root:/usr/bin/false _uucp:*:4:4:Unix to Unix Copy Protocol:/var/spool/uucp:/usr/sbin/uucico _taskgated:*:13:13:Task Gate Daemon:/var/empty:/usr/bin/false）选项：

-v

<强>输出：

grep "^\s*#"

使用您的命令# User Database # # Note that this file is consulted directly only when the system is running # in single-user mode. At other times this information is provided by # Open Directory. # # See the opendirectoryd(8) man page for additional information about # Open Directory. ##，您只能告诉grep （grep -Eo "[^#]+"）在没有＃的情况下匹配行的部分 - 所以它显然很明显除＃字符外，输出所有内容。

POSIX版本：

-o

使用否定排除包含`＃`

2 个答案: