C语言 打印 pid_t 的正确 printf 说明符是什么
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What is the correct printf specifier for printing pid_t
提问by Bilal Syed Hussain
I'm currently using a explicit cast to long and using %ldfor printing pid_t, is there a specifier such as %zfor size_tfor pid_t?
我目前使用一个显式的长和使用%ld打印pid_t，有一个符如%z用于size_t为pid_t？
If not what the best way of printing pid_t?
如果不是最好的打印方式是pid_t什么？
采纳答案by Jim Balter
There's no such specifier. I think what you're doing (casting the pid to longand printing it with "%ld") is fine; you could use an even wider int type, but there's no implementation where pid_tis bigger than longand probably never will be.
没有这样的说明符。我认为你在做什么（将 pid 投射到long并用“%ld”打印）很好；您可以使用更宽的 int 类型，但没有实现pid_t大于long并且可能永远不会的实现。
回答by chux - Reinstate Monica
With integer types lacking a matching format specifier as in the case of pid_t, yet with known sign-ness1, cast to widest matching signed type and print.
对于缺少匹配格式说明符的整数类型，如pid_t，但具有已知符号1，转换为最广泛匹配的有符号类型并打印。
If sign-ness is not known, cast to the widest unsigned type or alternate opinion
如果符号未知，则转换为最宽的无符号类型或替代意见
pid_t pid = foo();
// C99
#include <stdint.h>
printf("pid = %jd\n", (intmax_t) pid);
Or
或者
// C99
#include <stdint.h>
#include <inttypes.h>
printf("pid = %" PRIdMAX "\n", (intmax_t) pid);
Or
或者
// pre-C99
pid_t pid = foo();
printf("pid = %ld\n", (long) pid);
1The pid_tdata type is a signed integertype which is capable of representing a process ID.
1的pid_t数据类型是一个带符号的整数，其能够表示进程ID的类型。
