Login or Register to Ask a Question and Join Our Community


UNIX for Dummies Questions & Answers

/dev/fd question

 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers /dev/fd question
# 1  
Old 11-19-2009
/dev/fd question
what exactly is going on in this piece of code? what is the role of /dev/fd? i know that /dev/fd/0 is somehow linked to standard input, but that's the extent of my knowledge

Code:
cat header.txt /dev/fd/0 footer.txt

# 2  
Old 11-20-2009
Code:
$> cat header.txt
This is the Header
------------------

$> cat footer.txt
------------------
This is the Footer

$> echo bla bla bla|cat header.txt /dev/fd/0 footer.txt
This is the Header
------------------
bla bla bla
------------------
This is the Footer

$> echo bla bla bla|cat header.txt - footer.txt
This is the Header
------------------
bla bla bla
------------------
This is the Footer

# 3  
Old 11-20-2009
hey scrutinizer.

yeah i just figured it out. basically it takes input from the previous pipe, right?
 
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Red Hat

Changing grub from /dev/sda to /dev/sdb

Hi, Please suggest steps to change grub from /dev/sda to /dev/sdb, (1 Reply)
Discussion started by: manoj.solaris
1 Replies

2. Shell Programming and Scripting

Automating partitioning setup of /dev/sda on /dev/sdc

Objective: To recreate the partitioning setup of /dev/sda on /dev/sdc How would I parse the below information and initialize variables (an array?) that can be used to build sgdisk commands in a script, regardless of the number of partitions? Something along the lines of: sgdisk -n... (12 Replies)
Discussion started by: RogerBaran
12 Replies

3. AIX

Problem in /dev/hd1 and /dev/hd9var

Hello AIXians, I can't boot my AIX, it hangs and stops at the code error: 0518 After searching google, I knew the problem is due to problems in File Systems. So the solution is booting from any bootable media, then run these commands in maintenance mode: #fsck -y /dev/hd4 #fsck -y... (3 Replies)
Discussion started by: Mohannad
3 Replies

4. Shell Programming and Scripting

Simply question about capturing output to /dev/tty

Suppose another person wrote the following one-line shell script: echo $RANDOM > /dev/tty QUESTION #1: How can the random number, which is output to the terminal by this script, be captured in a variable? QUESTION #2: How can this be done in a cron job? Specific code, whether in ksh or... (1 Reply)
Discussion started by: Paul R
1 Replies

5. AIX

Difference between /dev/hdisk and /dev/rhdisk

Hi, How can i check that i am using RAW devices for storage in my AIX machine... Also after adding a LUN from storage to a aix host, when i check /dev in the host, i can see both rhdisk and hdisk with same number eg: dcback1(root):/dev>ls -lrt | grep disk12 crw------- 1 root ... (4 Replies)
Discussion started by: jibujacob
4 Replies

6. Solaris

Lun remove, stuck in /dev/dsk and /dev/rdsk

So, we removed a LUN from the SAN and the system is refusing to remove the references to it in the /dev folder. I've done the following: devfsadm -Cv powermt -q luxadm -e offline <drive path> luxadm probe All those commands failed to remove the path. The drive stills shows up as <drive... (13 Replies)
Discussion started by: DustinT
13 Replies

7. UNIX for Dummies Questions & Answers

Help Understanding Output and question about /dev/

Hi, I am having some problems understanding the info from the following output: Disk /dev/sda: 17849 cylinders, 255 heads, 63 sectors/track Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0 Device Boot Start End #cyls #blocks Id System /dev/sda1 *... (5 Replies)
Discussion started by: mojoman
5 Replies

8. Solaris

What is /dev/tty /dev/null and /dev/console

Hi, Anyone can help My solaris 8 system has the following /dev/null , /dev/tty and /dev/console All permission are lrwxrwxrwx Can this be change to a non-world write ?? any impact ?? (12 Replies)
Discussion started by: civic2005
12 Replies

9. UNIX for Dummies Questions & Answers

/dev question

RH 7.2 My machine has an LCD screen on the front of the panel. I've been given software to control some text on the LCD. The software checks /dev/tts/1 for the LCD. Since I don't have any /dev/tts directory, the developer told me just to make a link from the LCD to /dev/tts/1, but I don't... (4 Replies)
Discussion started by: jalburger
4 Replies

10. UNIX for Dummies Questions & Answers

/dev/null 2>&1 question

Hi, suppose you have the following line at your crontab : 5 * * * * /usr/mine/script > /dev/null 2>&1 now i understood that the " > /dev/null 2>&1 outputs both Standard outpout and Standard Error messages to the /dev/null device or file... the first part , " > /dev/null " transfers... (1 Reply)
Discussion started by: BAM
1 Replies
Login or Register to Ask a Question