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It says that ino_t is an unsigned integer type used for file serial numbers. For both uid_t and gid_t, it says that the type is an integer type (no mention of signed or unsigned) used for user IDs and group IDS. Thus, the standard clearly states that the type of uid_t and gid_t can be signed or unsigned depending on the platform. It is very ...
In other words, uid_t and gid_t are unsigned 32-bit integers and pid_t is a signed 32-bit integer. This applies for both 32- and 64-bits. I am not sure what they are on other architectures offhand as I don't have any available at the moment, but the definitive way is to compile a program which prints the output of sizeof(uid_t), etc.
struct passwd *getpwuid(uid_t uid); int getpwuid_r(uid_t uid, struct passwd *pwbuf, char *buf, size_t buflen, struct passwd **pwbufp); The getpwuid() function returns a pointer to a structure containing the broken-out fields of the record in the password database that matches the user ID uid.
In older Posix standards, pid_t was only defined in , but since Posix.1-2001 (Issue 7) it is also in . However, in order to get definitions in Posix.1-2001, you must define an appropriate feature test macro before including any standard header file. So either of the following two sequences will work:
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Linux下time_t时间类型 time_t类型定义在time.h头文件中： #ifndef __TIME_T #define __TIME_T typedef long time_t; #endif 可见，time_t实际是一个长整型。 其值表示为从UTC(coordinated universal time)时间1970年1月1日00时00分00秒(也称为L
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There is no format specifier for __uid_t, because this type is system-specific and is not the part of C standard, and hence printf is not aware of it. The usual workaround is to promote it to a type that would fit the entire range of UID values on all the systems you are targeting:
size_t and off_t are just unsigned integral types. (Edit: off_t is a long? See, the lesson is, check your headers!) So use sprintf (or whatever) to convert them using the "%i" format specifier. On edit: crap, you changed size_t to uid_t while I was answering. uid_t is defined in types.h; look there.
以下内容是CSDN社区关于关于Linux中使用geteuid()返回值uid_t参数值的问题相关内容，如果想了解更多关于Linux_Kernel社区其他内容，请访问CSDN社区。 刚学不久linux，写who am i的时候发现网上不少答案用的都是geteuid（）获得有效用户，看了下man帮助，这么显示的：