无法访问expect_background中的变量

Question

我有这个代码启动一个进程，expect一些启动输出，然后将其余的记录到文件中：

proc foo { } {
    set log_fp [open "somefile" a]

    exec cp $prog "$prog.elf"

    spawn someprog
    set someprog_spawn_id $spawn_id

    # do some things here that that wait for output from someprog
    expect {
        -i $someprog_spawn_id
        -re "Some output indicating successful startup"
    }

    # send the process into the background
    expect_background {
        -i $someprog_spawn_id
        full_buffer { }
        eof {
            wait -i $someprog_spawn_id
            close $log_fp 
        }
        -re {^.*\n} {
            puts $log_fp $expect_out(buffer)
        }
    }
}

不幸的是，这个错误与消息：

can't read "log_fp": no such variable

如何在此范围内访问此变量？

Answer 1

expect_background回调脚本在全局范围内进行评估（因为该过程很可能在它们触发时完成）所以你必须将变量放在该范围内......

proc foo { } {
    global log_fp
    set log_fp [open "somefile" a]
    # ...

或者，对于8.5，您可以使用apply来制作绑定

expect_background "
    -i \$someprog_spawn_id
    full_buffer { }
    [list eof [list apply {log_fp {
        wait -i $someprog_spawn_id
        close $log_fp 
    }} $log_fp]]
    [list -re {^.*\n} [list apply {log_fp {
        puts $log_fp $expect_out(buffer)
    }} $log_fp]]
"

真的很丑陋。使用全局变量要容易得多。