Use getpwnam group of functions. Example code: #include <sys/types.h> #include <pwd.h> #inc... For gid, use getgrnam

execl takes the full path name of the command and variable length of arguments terminated by NULL: execl("/bin/ls", "/bin/ls", "-r", "-t", "-l", NULL... where the second argument is argv[0] , but can be any string! execlp will try to find the command from $PATH , so full path to command is not needed: execl("ls", "ls", "-r", "-t", "-l", NULL); execv is the equivalent of execl , except that the arguments are passed in as a NULL terminated array: char *args[] = {"/bin/ls", "-r", "-t", "-l", NULL ... execvp is the equivalent of execvl , excep that the arguments are passed in as a NULL terminated array: char *args[] = {"ls", "-r", "-t", "-l", NULL }; ...

I don't know if there's a fool proof way to find out which Linux distro you are running on, but here are some ways you can try: cat /proc/version cat /etc/issue cat /etc/*release lsb_release -a Results on Ubuntu 11.10 oneiric: $ cat /proc/version Linux version 3.0.0-13-gene... Results on Red Hat Enterprise Server: $ cat /proc/version Linux version 2.6.18-128.1....

Unix hidden files are named starting with a dot ".". To find hidden files in the current directory: $ find . -type f -name '.*' or $ find . -type f | grep \\/\\. To find hidden files in the marketing directory: $ find marketing -type f -name '.*' or $ find marketing -type f | grep \\/\\.

A naive try would be something like this: $ nc -l 8082 | nc remote_host 80 Yes, it does forward the request from local port 8082 to remote_host:80 , but the response is dumped to stdout , not routed back to the client as expected. Using a named pipe makes it work: $ mkfifo backpipe $ nc -l 8082 0<backpipe | nc ... Use tee to get a glimpse of the response through the pipe (I wasn't able to find a way to dump the request): $ nc -k -l 8082 0<backpipe | nc localhost 80 | tee... The GNU netcat has a different syntax than the stock nc . It also supports different switches. To listen to port 1234: $ netcat -l -p 1234...

These steps set up a Linux host as IPSec client, using Openswan . Install Openswan: # yum install openswan Edit /etc/ipsec.conf . Instead of L2TP on port 1701, I'm setting up TCP on port 8080 so that I can test the connection with nc . # /etc/ipsec.conf - Openswan IPsec configuration f... Edit /etc/ipsec.secrets . # include /etc/ipsec.d/*.secrets 192.168.0.101 ... Start IPSec: # /etc/init.d/ipsec start Connect to IPSec server: # ipsec auto --up TCP8080-PSK-CLIENT 104 "TCP80...

The bash environment variable PROMPT_COMMAND contains a regular bash command that is executed just before the command prompt is displayed. For example: $ export PROMPT_COMMAND=a bash: a: command not ... The command a is not valid so you get the error message every time you hit enter. Echo something before $PS1 : $ export PROMPT_COMMAND='echo -n Hi!' Hi!$ ... PROMPT_COMMAND is regularly used to change the xterm window title. You may find this in /etc/bashrc : case $TERM in xterm*) if [ -...

GNU cpio copies files into or out of a cpio or tar archive. There are 3 modes: -o : copy-out mode, copies files into an archive -i : copy-in mode, copies files out of an archive -p : copy-pass mode, combines the copy-out and copy-in steps without actually using an archive Examples: # create a cpio archive with all files in the ...

This worked: gcc hello.c But this failed: gcc -static hello.c /usr/bin/ld: cannot find -l... I was missing static glibc libraries. Installed the static libraries with: yum install glibc-static Verify with ldd : ldd a.out not a dynamic executable

On Linux, you can use the fuser command to find out who has a file open, or is using a port. For example, if you start Tomcat and get the error "Address already in use: 8080", you want to know which process is already binding to port 8080. # list processes on port 8080 fuser 8080/tcp ...

I was experiencing extreme slow DNS lookup on my wireless network when using Firefox on my FC4 installation. I found some discussions on the Apple discussion group and the Fedora forum but I wasn't able to find much help for my situation. I then looked at the DNS entries configured by the DHCP service and it was listing the IP addresses of my wireless router and DSL modem. I disabled automatic DNS setup and manually entered the name servers in /etc/resolv.conf . It's now much faster. I booted my laptop to Windows, the DHCP assigned DNS entries remained the same (wireless router and DSL modem). But I didn't have any problems with either Firefox or IE. This seems to be a Linux (maybe FC4?) only