以下是我的shell脚本:
#!/bin/sh
exec 100>&1
exec 1>hello.txt
echo "hello exec"
echo "hello world"
exec 1>&100 100>&-
但当我运行它时,系统提示如下:
exec: 2: 100: not found
当我使用命令lsof
来检查它的文件描述符信息时,它会提示:
lsof -p 31931 -d 100
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
dbus-daem 1230 kaiwii 100u unix 0x00000000 0t0 3753938 socket
bash 31931 kaiwii cwd DIR 8,7 4096 6316395 /home/kaiwii/test
bash 31931 kaiwii rtd DIR 8,7 4096 2 /
bash 31931 kaiwii txt REG 8,7 822420 8208388 /bin/bash
bash 31931 kaiwii mem REG 8,7 1434180 1688385 /lib/i386-linux-gnu/libc-2.13.so
bash 31931 kaiwii mem REG 8,7 38500 1688435 /lib/i386-linux-gnu/libnss_nis-2.13.so
bash 31931 kaiwii mem REG 8,7 79672 1688425 /lib/i386-linux-gnu/libnsl-2.13.so
bash 31931 kaiwii mem REG 8,7 26400 1688427 /lib/i386-linux-gnu/libnss_compat-2.13.so
bash 31931 kaiwii mem REG 8,7 117960 1688372 /lib/i386-linux-gnu/ld-2.13.so
bash 31931 kaiwii mem REG 8,7 9736 1688395 /lib/i386-linux-gnu/libdl-2.13.so
bash 31931 kaiwii mem REG 8,7 223468 1687611 /lib/libncurses.so.5.7
bash 31931 kaiwii mem REG 8,7 42580 1688431 /lib/i386-linux-gnu/libnss_files-2.13.so
bash 31931 kaiwii mem REG 8,7 123384 5685786 /usr/share/locale-langpack/zh_CN/LC_MESSAGES/bash.mo
bash 31931 kaiwii mem REG 8,7 8322432 319489 /usr/lib/locale/locale-archive
bash 31931 kaiwii 0r CHR 136,0 0t0 3 /dev/pts/0
bash 31931 kaiwii 1u CHR 136,0 0t0 3 /dev/pts/0
bash 31931 kaiwii 2u CHR 136,0 0t0 3 /dev/pts/0
bash 31931 kaiwii 255u CHR 136,0 0t0 3 /dev/pts/0
因为我对 exec
命令尤其是如何修改文件描述符不熟悉,所以我不知道发生了什么事情!顺便说一下,当我将文件描述符从100改为8时,它可以正常运行!
exec
内置函数提供了一种将输入和输出重定向到文件描述符的机制。 - Adam Liss