列表输出被截断 如何在 R 中使用 str() 扩展列出的变量

我有数据.第df帧包含600多个变量.我正在编写一个函数，可以自动创建列，并且需要对它们进行一次视觉判断.

str函数提供了一个很好的总结:

str(df)
'data.frame':   29 obs. of  602 variables:
 $ uniqueSessionsIni: POSIXct, format: "2015-01-05 15:00:00" "2015-01-05 16:00:00" "2015-01-05 17:00:00" ...
 $ uniqueSessionsEnd: POSIXct, format: "2015-01-05 15:59:00" "2015-01-05 16:59:00" "2015-01-05 17:59:00" ...
 $ m0p0             : POSIXct, format: "2015-01-05 15:00:00" "2015-01-05 15:00:00" "2015-01-05 15:00:00" ...
 $ m1p0             : POSIXct, format: "2015-01-05 15:01:00" "2015-01-05 15:01:00" "2015-01-05 15:01:00" ...
 $ m2p0             : POSIXct, format: "2015-01-05 15:02:00" "2015-01-05 15:02:00" "2015-01-05 15:02:00" ...    

然后继续

$ m33p1            : POSIXct, format: "2015-01-05 15:34:00" "2015-01-05 15:34:00" "2015-01-05 15:34:00" ...
$ m34p1            : POSIXct, format: "2015-01-05 15:35:00" "2015-01-05 15:35:00" "2015-01-05 15:35:00" ...
$ m35p1            : POSIXct, format: "2015-01-05 15:36:00" "2015-01-05 15:36:00" "2015-01-05 15:36:00" ...
$ m36p1            : POSIXct, format: "2015-01-05 15:37:00" "2015-01-05 15:37:00" "2015-01-05 15:37:00" ...
[list output truncated]

如何显示602个变量的完整列表？