I wrote a very simple (my first) c program. when I compile it using the following command: gcc test.c -o ./test I get these error messages: /data1/AIPSDATA/cccOR2AB.o: In function `main': /data1/AIPSDATA/cccOR2AB.o(.text+0xfe): undefined reference to `sqrt' collect2: ld returned 1 exit status AIPS is an astronomical data reduction software I installed a while back, and /data1/AIPSDATA/ is a subdirectory used to store AIPS file. It has nothing to do with this c program I've written. I've also tried compiling using the following command: g++ -lm test.c -o ./test This gave me the following error messages: /data1/AIPSDATA/ccmttbnu.o: In function `main': /data1/AIPSDATA/ccmttbnu.o(.text+0xfe): undefined reference to `sqrt' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `cosh@GLIBC_2.0' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `cos@GLIBC_2.0' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `exp@GLIBC_2.0' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `sinh@GLIBC_2.0' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `sin@GLIBC_2.0' /usr/lib/gcc-lib/i386-redhat-linux/2.96/libstdc++.so: undefined reference to `log@GLIBC_2.0' collect2: ld returned 1 exit status Can anyone help with this mysterious problem? Siow-Wang

It appears that it's trying to link the cccOR2AB.o file. Can you show us the code for test.c?

Just at a glance... it looks like you are missing the math header file. Infinite Recursion

are you in the right directory when you compile? i use this command to compile: g++ -o test test.cpp ~ and then to run ./test

When I compiled the code (given below), I was in the subdirectory where the code is located, which is /data1/n5775/. I have also sent the code to a friend's computer and was able to compile it successfully there. #include #include int main(void) { float vel1,vel2,ii,rms,ii_rms; char l[80],offset[10]; int i; FILE *fp,*fp2; fp = fopen("co10iram_integrated_intensity_table.dat","r"); fp2 = fopen("co10iram_rms_integrated_intensity.dat","w"); /* bypassing file comments */ for (i=0; i18; ++1) fgets(l,80,fp); /* reading in data and calculating rms of integrated intensity */ while (fgets(l,100,fp) != NULL) { sscanf(l,"%c %f %f %f %f",&offset,&vel1,&vel2,&ii,&rms); ii_rms = sqrt((vel2-vel1)/3.269)*3.269*rms; fprintf(fp2,"%c %f %f %f %f \n",&offset,&vel1,&vel2,&ii,&ii_rms); } } Also, what's the math header file? (response 2) I don't understand the command g++ -o test test.cpp ~ (response 3). Pray explain. Thanks very much. Siow-Wang

#include #include int main(void) { float vel1,vel2,ii,rms,ii_rms; char l[80],offset[10]; int i; FILE *fp,*fp2; fp = fopen("co10iram_integrated_intensity_table.dat","r"); fp2 = fopen("co10iram_rms_integrated_intensity.dat","w"); /* bypassing file comments */ for (i=0; i18; ++1) fgets(l,80,fp); /* reading in data and calculating rms of integrated intensity */ while (fgets(l,100,fp) != NULL) { sscanf(l,"%c %f %f %f %f",&offset,&vel1,&vel2,&ii,&rms); ii_rms = sqrt((vel2-vel1)/3.269)*3.269*rms; fprint(fp2, "%c %f %f %f %f \n",&offset,&vel1,&vel2,&ii,&ii_rms); } }

sorry about the repeats, but I can't seem to get the code printed out properly here. Anyway, the stdio.h and math.h were in the include statements where they should be. Siow-Wang