Shell standard error redirection to standard output

Shell standard error redirection to standard output 2 & gt; & amp; 1 is to redirect standard errors to standard output the second problem is very simple: use this command to achieve: cat/etc/passwd | greproot | cut-d & quot;: & quot;-f1 :~ $ Cat/etc/passwd... shell standard error redirection to standard output 2> & 1 is to redirect standard errors to standard output the second problem is simple: use this command to achieve: cat/etc/passwd | grep root | cut-d ":"-f1 implementation :~ $ Cat/etc/passwd | grep root | cut-d ":"-f1 root. what do you mean? Q: Yes. what does this mean? what does this operator mean? Save it. Answer> it means output redirection.> Rewrite in overwrite mode> append mode. 1 indicates the standard output, and 2 indicates the error message output. & 1 indicates the standard output. The last & symbol indicates the backend execution. Let me look for an example. please study it with patience: ls hanls: Cannot access han: no file or directory for execution ~ $ Ls han> 1.txt 2> & 1 is not displayed in shell. then execute ~ $ Cat 1.txt ls: inaccessible han: No such file or directory description error information is redirected to the 1.txt file. If this & ls han> 1.txt 2> 1 is not added, another 1 file will be generated. Cat 1ls: unable to access han: there is no such file or directory. & 1 indicates the logical standard output. Without adding &, a file named 1 will be generated.