特殊文件句柄
perl提供了6种特殊的文件句柄:
STDIN ，
STDOUT ，
STDERR ，
DATA ，
ARGV，
ARGVOUT。
访问模式
| 模式 | 描述 |
| < 或 r | 只读方式打开，将文件指针指向文件头。 |
| > 或 w | 写入方式打开，将文件指针指向文件头并将文件大小截为零。如果文件不存在则尝试创建之。 |
| >> 或 a | 写入方式打开，将文件指针指向文件末尾。如果文件不存在则尝试创建之。 |
| +< 或 r+ | 读写方式打开，将文件指针指向文件头。 |
| +> 或 w+ | 读写方式打开，将文件指针指向文件头并将文件大小截为零。如果文件不存在则尝试创建之。 |
| +>> 或 a+ | 读写方式打开，将文件指针指向文件末尾。如果文件不存在则尝试创建之。 |
文件测试
| File Test | Meaning |
| -r | File or directory is readable by this (effective) user or group |
| -w | File or directory is writable by this (effective) user or group |
| -x | File or directory is executable by this (effective) user or group |
| -o | File or directory is owned by this (effective) user |
| -R | File or directory is readable by this real user or group |
| -W | File or directory is writable by this real user or group |
| -X | File or directory is executable by this real user or group |
| -O | File or directory is owned by this real user |
| -e | File or directory name exists |
| -z | File exists and has zero size (always false for directories) |
| -s | File or directory exists and has nonzero size (the value is the size in bytes) |
| -f | Entry is a plain file |
| -d | Entry is a directory |
| -l | Entry is a symbolic link |
| -S | Entry is a socket |
| -p | Entry is a named pipe (a “fifo”) |
| -b | Entry is a block-special file (like a mountable disk) |
| -c | Entry is a character-special file (like an I/O device) |
| -u | File or directory is setuid |
| -g | File or directory is setgid |
| -k | File or directory has the sticky bit set |
| -t | The filehandle is a TTY (as reported by the isatty() system function; filenames can’t be tested by this test) |
| -T | File looks like a “text” file |
| -B | File looks like a “binary” file |
| -M | Modification age (measured in days) |
| -A | Access age (measured in days) |
| -C | Inode-modification age (measured in days) |
if (-r $filename and -w $filename) {
... }
- 文件测试操作符没写文件名和文件句柄,则默认文件名保存在$_里
foreach (@lots_of_filenames) {
print "$_ is readable\n" if -r;
}
select
使用select更改默认文件输出句柄