How to list the open file descriptors (and the files they refer to) in my current bash session
I am running in an interactive bash session. I have created some file descriptors, using exec, and I would like to list what is the current status of my bash session. Is there a way to list the currently open file descriptors?
bash is not part of the kernel, so it can not know what other processes are doing, even those that it started.
@JuliePelletier: but child processes do not change the file descriptors of the parent process, do they?
5 Answers 5
Yes, this will list all open file descriptors:
$ ls -l /proc/$$/fd total 0 lrwx------ 1 isaac isaac 64 Dec 28 00:56 0 -> /dev/pts/6 lrwx------ 1 isaac isaac 64 Dec 28 00:56 1 -> /dev/pts/6 lrwx------ 1 isaac isaac 64 Dec 28 00:56 2 -> /dev/pts/6 lrwx------ 1 isaac isaac 64 Dec 28 00:56 255 -> /dev/pts/6 l-wx------ 1 isaac isaac 64 Dec 28 00:56 4 -> /home/isaac/testfile.txt Of course, as usual: 0 is stdin, 1 is stdout and 2 is stderr.
The 4th is an open file (to write) in this case.
@JZ. $$ will give the process ID of the currently running shell. Try echo $$ and ps and compare their outputs. Similar question here.
Assuming you want to list the file descriptors that are attached to any terminal, you can use lsof / fuser or similar like:
$ lsof -p $$ 2>/dev/null | awk '$NF ~ /\/pts\//' bash 32406 foobar 0u CHR 136,31 0t0 34 /dev/pts/31 bash 32406 foobar 1u CHR 136,31 0t0 34 /dev/pts/31 bash 32406 foobar 2u CHR 136,31 0t0 34 /dev/pts/31 bash 32406 foobar 3u CHR 136,31 0t0 34 /dev/pts/31 bash 32406 foobar 255u CHR 136,31 0t0 34 /dev/pts/31 These tools basically parse /proc , so you can just access /proc/$$/fd/ too e.g.:
Use the lsof utility to print all file descriptors for the current shell process (process identified by -p $$ ) and ( -a ) where the file descriptor is numeric ( -d 0-256 ):
$ lsof -p $$ -a -d 0-256 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME bash 16883 ant 0u CHR 136,15 0t0 18 /dev/pts/15 bash 16883 ant 1u CHR 136,15 0t0 18 /dev/pts/15 bash 16883 ant 2u CHR 136,15 0t0 18 /dev/pts/15 bash 16883 ant 255u CHR 136,15 0t0 18 /dev/pts/15 Pipe into Awk to print only the file descriptor and its corresponding filename:
$ lsof -p $$ -a -d 0-256 | awk '< printf("%4s:\t%s\n", $4, $NF) >' FD: NAME 0u: /dev/pts/15 1u: /dev/pts/15 2u: /dev/pts/15 255u: /dev/pts/15 Note: when lsof prints the file descriptors, it appends the following code to indicate the file access mode: