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  1. Linux学习笔记——有效群组(effective group)与初始群组(initial group)

    Wed 18 December 2013   Write By xymelon

    有效群组(effective group)与初始群组(initial group)

    初始群组:/etc/passwd中第四栏所标志的GID;当用户登入系统,立刻拥有该群组的相关权限。

    有效群组:当以某个用户身份登入后,输入groups命令第一出现的群组即为有效群组。它的作用是当用户建立新文件或目录时,所属群组为有效群组。

    Tagged as : Linux
  2. Linux学习笔记——'Pattern Space' and 'Hold Space' in sed

    Mon 02 December 2013   Write By xymelon

    来源:http://stackoverflow.com/questions/12833714/the-concept-of-hold-space-and-pattern-space-in-sed

    When sed reads a file line by line, the line that has been currently read is inserted into the pattern buffer (pattern space). Pattern buffer is like the temporary buffer, the scratchpad where the current information is stored. When you tell sed to print, it prints the pattern buffer.

    Hold buffer / hold space is like a long-term storage, such that you can catch something, store it and reuse it later when sed is processing another line. You do not directly process the hold space, instead, you need to copy it or append to the pattern space if you want to do something with it. For example, the print command p prints the pattern space only. Likewise, s operates on the pattern space.

    Tagged as : Linux
  3. Linux学习笔记——权限管理(2)

    Sat 23 November 2013   Write By xymelon

    特殊文件权限:SUID,SGID,SBIT

    SUID:当s这个标志出现在文件拥有者权限的x权限上时,如【-rwsr-xr-x】,此时被称为Set UID,简称为SUID的特殊权限,且只对文件有效。

    1. SUID权限仅对二进制程序(binary program)有效;
    2. 执行者对于该程序需要具有x的可执行权限;
    3. 本权限尽在执行该程序的过程中有效(run-time);
    4. 执行者将具有该拥有者(owner)的权限。
    Tagged as : Linux

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