我正在尝试在我的 crontab 文件中附加一行。我知道还有其他方法可以解决这个问题,但仍然想知道是什么原因造成的。该命令在树莓派 3 B+ 上运行,安装了 raspbian lite,GNU ed 1.15,cron 3.0pl1-134+deb10u1。
我坚持的命令是:
$ echo -e 'a\n#asdf\n.\nwQ' | EDITOR=ed crontab -e
902
909
No modification made
我希望它#asdf
在我的 crontab 文件末尾添加行,但事实并非如此。
按照https://stackoverflow.com/a/30123606/8842387EDITOR='tee -a'
上的建议进行设置并不能解决问题。所以我想这是cron的问题。
奇怪的是,当我直接从键盘发出 ed 命令而不是流式传输它时,它就可以工作了。也许子shell创建导致了问题?
在这里,我附上了strace
结果中的最后几行。
$ echo -e 'a\n#asdf\n.\nwQ' | EDITOR=ed strace crontab -e
execve("/usr/bin/crontab", ["crontab", "-e"], 0x7ee54c14 /* 29 vars */) = 0
access("/etc/suid-debug", F_OK) = -1 ENOENT (No such file or directory)
...
read(3, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\7\0\0\0\7\0\0\0\0"..., 4096) = 659
_llseek(3, -393, [266], SEEK_CUR) = 0
read(3, "TZif2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\7\0\0\0\7\0\0\0\0"..., 4096) = 393
close(3) = 0
getpid() = 18579
socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0) = 3
connect(3, {sa_family=AF_UNIX, sun_path="/dev/log"}, 110) = 0
send(3, "<78>Nov 20 15:31:25 crontab[1857"..., 56, MSG_NOSIGNAL) = 56
openat(AT_FDCWD, "crontabs/pi", O_RDONLY) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 4
fstat64(4, {st_mode=S_IFREG|0644, st_size=2995, ...}) = 0
read(4, "# Locale name alias data base.\n#"..., 4096) = 2995
read(4, "", 4096) = 0
close(4) = 0
openat(AT_FDCWD, "/usr/share/locale/en_GB.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_GB.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_GB/LC_MESSAGES/libc.mo", O_RDONLY) = 4
fstat64(4, {st_mode=S_IFREG|0644, st_size=1433, ...}) = 0
mmap2(NULL, 1433, PROT_READ, MAP_PRIVATE, 4, 0) = 0x76f50000
close(4) = 0
openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "crontabs/pi/: fdopen: Permission"..., 39crontabs/pi/: fdopen: Permission denied) = 39
exit_group(1) = ?
+++ exited with 1 +++
openat(AT_FDCWD, "crontabs/pi", O_RDONLY) = -1 EACCES (Permission denied)
看起来有点可疑,但不确定为什么它以只读方式打开文件。
编辑:正如@tink 所建议的,我跑去EDITOR=ed strace crontab -e
看看strace
在交互式会话中给出了什么。结果几乎相同(仅在 pid 和 fd 编号上有所不同)。
我注意到运行echo "..." | EDITOR=ed crontab -e
退出并显示消息No modification made
,但strace
进程停止但没有任何消息。(EDITOR=ed strace crontab -e 2>&1 | grep "No mod"
什么都不打印)。猜猜 strace 会触发不同的错误。