Support truncating dead file descriptors

It is a common needed functionality for leaky services to be able to
easily zero out their dead file descriptors to prolong service lifetime
before a reboot is needed. This adds the switch `--truncate-dead` which
will cause fd-enum to truncate all dead file descriptors to zero length.
This saves effort and runtime where previously the list of dead
descriptors would need to be parsed and piped to another program for
zeroing. This is much faster.

1 files changed, 22 insertions, 15 deletions

diff --git a/main.c b/main.c
index 1921e14..f3b7459 100644
--- a/main.c
+++ b/main.c
@@ -30,6 +30,7 @@ struct config {
   char inodes;
   char pipes;
   char showstats;
+  char truncate_dead;
 };
 
 int fexists(char* path) {
@@ -42,31 +43,35 @@ int fexists(char* path) {
 
 void get_help() {
   puts("Usage: \n\
-  -d, --dead     Print list of dead file descriptors (deleted but still open)\n\
-  -i, --inodes   Print list of inode file descriptors\n\
-  -l, --live     Print list of live file descriptors (open and existing)\n\
-  -p, --pipes    Print list of pipe file descriptors\n\
-  -s, --sockets  Print list of socket file descriptors\n\
+  -d, --dead       Print list of dead file descriptors (deleted but still open)\n\
+  -i, --inodes     Print list of inode file descriptors\n\
+  -l, --live       Print list of live file descriptors (open and existing)\n\
+  -p, --pipes      Print list of pipe file descriptors\n\
+  -s, --sockets    Print list of socket file descriptors\n\
 \n\
-  -n, --no-stats Hide file descriptor statistics\n\
-  -h, --help     Print this help text\n\
+  -n, --no-stats   Hide file descriptor statistics\n\
+  --truncate-dead  Truncate dead file descriptors\n\
+  -h, --help       Print this help text\n\
 ");
 }
 
 int parse_args(int argc, char* argv[], struct config* c) {
   // Initialize config struct
-  c->pid       = -1;
-  c->dead      = 0;
-  c->live      = 0;
-  c->sockets   = 0;
-  c->pipes     = 0;
-  c->inodes    = 0;
-  c->showstats = 1;
+  c->pid           = -1;
+  c->dead          = 0;
+  c->truncate_dead = 0;
+  c->live          = 0;
+  c->sockets       = 0;
+  c->pipes         = 0;
+  c->inodes        = 0;
+  c->showstats     = 1;
   int i = 1;
 
   while(i < argc) {
     if(strcmp(argv[i], "-d") == 0 || strcmp(argv[i], "--dead") == 0) {
       c->dead = 1;
+    } else if(strcmp(argv[i], "--truncate-dead") == 0) {
+      c->truncate_dead = 1;
     } else if(strcmp(argv[i], "-l") == 0 || strcmp(argv[i], "--live") == 0) {
       c->live = 1;
     } else if(strcmp(argv[i], "-s") == 0 || strcmp(argv[i], "--sockets") == 0) {
@@ -102,7 +107,7 @@ int main(int argc, char* argv[]) {
   char lnpath[512]    = {'\0'};
   int retval = 0;
   int len    = 0;
-  unsigned long unknown  = 0;
+  unsigned long unknown = 0;
   unsigned long dead    = 0;
   unsigned long live    = 0;
   unsigned long sockets = 0;
@@ -163,6 +168,8 @@ int main(int argc, char* argv[]) {
         dead++;
         if(c.dead)
           printf("%s -> %s\n", fdpath, lnpath);
+        if(c.truncate_dead)
+          truncate(fdpath, 0);
       }
 
     // Inodes